Big Ideas Math Book 1st Grade Answer Key Chapter 8 Add and Subtract Tens helps the students to overcome the difficulties in math. Learning in a fun way will make maths more interesting to students. You can see step-by-step explanations for all the questions by using the figures. You can easily understand the concepts deeply with the help of our Big Ideas Math Answers Grade 1 Chapter 8 Add and Subtract Tens.

## Big Ideas Math Book 1st Grade Answer Key Chapter 8 Add and Subtract Tens

In order to excel in the exam, we suggest the students of 1st standard refer to the Big Ideas Math Book 1st Grade Answer Key Chapter 8 Add and Subtract Tens. The topics shown in Big Ideas Math Answers Grade 1 Chapter 8 Add and Subtract Tens are as per the latest syllabus. Hit the links and start solving the problems using easy methods.

**Vocabulary**

**Lesson: 1 Mental Math: 10 More**

**Lesson: 2 Mental Math: 10 Less**

**Lesson: 3 Add Tens**

**Lesson: 4 Add Tens Using a Number Line**

**Lesson: 5 Subtract Tens**

**Lesson: 6 Subtract Tens Using a Number Line**

**Lesson: 7 Use Addition to Subtract Tens**

**Lesson: 8 Add Tens to a Number**

**Chapter: 8 Add and Subtract Tens**

### Add and Subtract Tens Vocabulary

**Organize It**

Review Words:

decade numbers

digits

Use the review words to complete the graphic organizer.

The ____________ of 16 are 1 and 6.

Answer:

The digits of 16 Are 1 and 6.

Explanation:

10, 20, 30, 40 and so on are decade numbers.

Any of the numerals from 0 to 9, especially when forming part of a number are called as digits.

**Define It**

What am I?

Answer:

Explanation:

13 – 3 = 10= B 4 + 4 = 8 = P

5 + 1 = 6 = O 3 + 2 = 5 = L

5 + 4 = 9 = I 12 – 8 = 4 = R

6 – 4 = 2 = M 10 – 3 = U

1 + 2 = 3 = E

9 – 8 = 1 = N

Hence , YOU are open number line.

### Lesson 8.1 Mental Math: 10 More

**Explore and Grow**

Find each sum. What do you notice?

13 + 10 = __________

39 + 10 = __________

52 + 10 = __________

Answer:

13 + 10 = 23

39 + 10 = 49

52 + 10 = 62

Explanation:

Addition is bringing two or more numbers (or things) together to make a new total.

The numbers to be added together are called the “Addends”:

1. Here, 13 and 10 are addends.

Now add both the numbers:

13 + 10 = 23.

2. Here, 39 and 10 are addends.

39 + 10 = 49.

3. Here, 52 and 10 are addends.

52 + 10 = 62.

Hence, its noticed that total number of groups are 10 in all the counters.

**Show and Grow**

Use mental math.

Question 1.

14 + 10 = __________

Answer:

14 + 10 = 24

Explanation:

Here, 14 and 10 are addends.

Now add both the numbers:

14 + 10 = 24.

Hence, Sum = 24.

Question 2.

46 + 10 = __________

Answer:

46 + 10 =56.

Explanation:

Here, 46 and 10 are addends.

Now add both the numbers:

46 + 10 = 56.

Hence, Sum = 56.

Question 3.

83 + 10 = __________

Answer:

83 + 10 = 93.

Explanation:

Here, 83 and 10 are addends.

Now add both the numbers:

83 + 10 = 93.

Hence, Sum = 93.

Question 4.

75 + 10 = __________

Answer:

75 + 10 = 85.

Explanation:

Here, 75 and 10 are addends.

Now add both the numbers:

75 + 10 = 85.

Hence, sum = 85.

Question 5.

21 + 10 = __________

Answer:

21 + 10 = 31.

Explanation:

Here, 21 and 10 are addends.

Now add both the numbers:

21 + 10 = 31.

Hence, Sum = 31.

Question 6.

60 + 10 = __________

Answer:

60 + 10 = 70.

Explanation:

Here, 60 and 10 are addends.

Now add both the numbers:

60 + 10 = 70.

Hence, Sum = 70.

Question 7.

10 + 89 = __________

Answer:

10 + 89 = 99.

Explanation:

Here, 10 and 89 are addends.

Now add both the numbers:

10 + 89 = 99.

Hence, Sum = 99.

Question 8.

10 + 68 = __________

Answer:

10 + 68 = 78.

Explanation:

Here, 10 and 68 are addends.

Now add both the numbers:

10 + 68 = 78.

Hence, Sum = 78.

**Apply and Grow: Practice**

Use Mental math.

Question 9.

16 + 10 = __________

Answer:

16 + 10 = 26.

Explanation:

Here, 16 and 10 are addends.

Now add both the numbers:

16 + 10 = 26.

Hence, Sum = 26.

Question 10.

63 + 10 = __________

Answer:

63 + 10 = 73.

Explanation:

Here, 63 and 10 are addends.

Now add both the numbers:

63 + 10 = 73.

Hence, Sum = 73.

Question 11.

8 + 10 = __________

Answer:

8 + 10 = 18.

Explanation:

Here, 8 and 10 are addends.

Now add both the numbers:

8 + 10 = 18.

Hence, Sum = 18.

Question 12.

44 + 10 = __________

Answer:

44 + 10 = 54.

Explanation:

Here, 44 and 10 are addends.

Now add both the numbers:

44 + 10 = 54.

Hence, Sum = 54.

Question 13.

19 + 10 = __________

Answer:

19 + 10 = 29.

Explanation:

Here, 19 and 10 are addends.

Now add both the numbers:

19 + 10 = 29.

Hence, Sum = 29.

Question 14.

59 + 10 = __________

Answer:

59 + 10 = 69.

Explanation:

Here, 59 and 10 are addends.

Now add both the numbers:

59 + 10 = 69.

Hence, Sum = 69.

Question 15.

10 + 22 = __________

Answer:

10 + 22 = 32.

Explanation:

Here, 10 and 22 are addends.

Now add both the numbers:

10 + 22 = 32.

Hence, Sum = 32.

Question 16.

10 + 50 = __________

Answer:

10 + 50 = 60.

Explanation:

Here, 10 and 50 are addends.

Now add both the numbers:

10 + 50 = 60.

Hence, Sum = 60.

Question 17.

10 + 71 = __________

Answer:

10 + 71 = 81.

Explanation:

Here, 10 and 71 are addends.

Now add both the numbers:

10 + 71 = 81.

Hence, Sum = 81.

Question 18.

10 + 38 = __________

Answer:

10 + 38 = 48.

Explanation:

Here, 10 and 38 are addends.

Now add both the numbers:

10 + 38 = 48.

Hence, Sum = 48.

Question 19.

55 + __________ = 65

Answer:

55 + _10__ = 65

Explanation:

Here, 55 and Missing number are addends.

Sum is given = 65

Let the missing number be X.

Now add the numbers:

55 + X= 65

X = 65 – 55

X = 10.

Hence, equation is 55 + 10 = 65.

Question 20.

87 + __________ = 97

Answer:

87 + __10__ = 97

Explanation:

Here, 87 and Missing number are addends.

Sum is given = 97

Let the missing number be X.

Now add the numbers:

87 + X = 97

X = 97 – 87

X = 10.

Hence, equation is 87 + 10 = 97.

Question 21.

**DIG DEEPER!**

Use each number once to complete the equations.

86 76 10 66

_________ + 10 = __________ ___________ + __________ = 96

Answer:

66 + 10 = 76

86 + 10 = 96

Explanation:

The numbers to be added together are called the “Addends”.

1. _________ + 10 = __________

We know among two addends, one is 10.

2. ___________ + __________ = 96

Given numbers 86,76,10,66.

Place every given number next to given addend 10:

86 + 10 = 96

76 + 10 = 86

10 + 10 = 20

66 + 10 =76.

Among this equations, for the first equation is 66 + 10 =76.

and the second is 86 + 10 = 96 because the it fulfills the given condition. (Use each number once to complete the equations.)

**Think and Grow: Modeling Real Life**

There are 33 students on a bus. 10 more get on. How many students are on the bus now?

Addition equation:

___________ students

Answer:

Total number of students on the bus now = 43.

Given:

Number of students in a bus = 33

Number of students more got into the bus = 10

Explanation:

Total number of students on the bus now = Number of students in a bus + Number of students more get into the bus = 33 + 10

= 43.

Hence, Total number of students on the bus now = 43.

**Show and Grow**

Question 22.

There are 61 tents at a campground. 10 more are put up. How many tents are at the campground now?

Addition equation:

____________ tents

Answer:

Number of tents at the campground now = 71.

Given:

Number of tents at a campground =61

Number of tents more put up at the campground= 10

Explanation:

Number of tents at the campground now = Number of tents at a campground – Number of tents more put up at the campground

= 61 + 10

= 71

Hence, Number of tents at the campground now = 71.

### Mental Math: 10 More Practice 8.1

Use Mental math.

Question 1.

30 + 10 = __________

Answer:

30 + 10 = 40

Explanation:

Here, 30 and 10 are addends.

Now add both the numbers:

30 + 10 = 40

Hence, Sum = 40.

Question 2.

81 + 10 = __________

Answer:

81 + 10 = 91

Explanation:

Here, 81 and 10 are addends.

Now add both the numbers:

81 + 10 = 91.

Hence, Sum = 91.

Question 3.

6 + 10 = __________

Answer:

6 + 10 = 16

Explanation:

Here, 6 and 10 are addends.

Now add both the numbers:

6 + 10 = 16.

Hence, Sum = 16.

Question 4.

57 + 10 = __________

Answer:

57 + 10 = 67

Explanation:

Here, 57 and 10 are addends.

Now add both the numbers:

57 + 10 = 67.

Hence, Sum = 67.

Question 5.

48 + 10 = __________

Answer:

48 + 10 = 58.

Explanation:

Here, 48 and 10 are addends.

Now add both the numbers:

48 + 10 = 58.

Hence, Sum = 58.

Question 6.

26 + 10 = __________

Answer:

26 + 10 = 36.

Explanation:

Here, 26 and 10 are addends.

Now add both the numbers:

26 + 10 = 36.

Hence, Sum = 36.

Question 7.

10 + 43 = __________

Answer:

10 + 43 = 53.

Explanation:

Here, 10 and 43 are addends.

Now add both the numbers:

10 + 43 = 53.

Hence, Sum = 53.

Question 8.

10 + 65 = __________

Answer:

10 + 65 = 75.

Explanation:

Here, 10 and 65 are addends.

Now add both the numbers:

10 + 65 = 75.

Hence, Sum = 75.

Question 9.

10 + 82 = __________

Answer:

10 + 82 = 92.

Explanation:

Here, 10 and 82 are addends.

Now add both the numbers:

10 + 82 = 92.

Hence, Sum = 92.

Question 10.

10 + 79 = __________

Answer:

10 + 79 = 89.

Explanation:

Here, 10 and 79 are addends.

Now add both the numbers:

10 + 79 = 89.

Hence, Sum = 89.

Question 11.

22 + __________ = 32

Answer:

22 + 10 =32.

Explanation:

Here, 22 and Missing number are addends.

Let the missing number be X.

Sum is given =32

Now add the numbers:

22 + X = 32

X = 32 – 22

X = 10.

Hence, equation is 22 + 10 =32.

Question 12.

85 + __________ = 95

Answer:

85 + 10 = 95.

Explanation:

Here, 85 and Missing number are addends.

Let the missing number be X.

Sum is given = 95

Add the numbers.

85 + X = 95

X = 95 – 85

X = 10.

Hence, equation is 85 + 10 = 95.

Question 13.

64 + __________ = 74

Answer:

64 + 10 = 74.

Explanation:

Here, 64 and Missing number are addends.

Let the missing number be X.

Sum is given = 74.

Add the numbers.

64 + X = 74

X = 74 – 64

X = 10.

Hence, equation is 64 + 10 = 74.

Question 14.

41 + __________ = 51

Answer:

41 + 10 = 51.

Here, 41 and Missing number are addends.

Let the missing number be X.

Sum is given = 51.

Add the numbers.

41 + X = 51

X = 51 – 41

X = 10.

Hence, equation is 41 + 10 = 51 .

Question 15.

**DIG DEEPER!**

Use each number once to complete the equations.

25 10 15 35

10 + __________ = _________ 25 + __________ = ___________

Answer:

10 + 15 = 25

25 +10 = 35

Explanation:

The numbers to be added together are called the “Addends”.

1. 10 + __________ = _________

2. 25 + __________ = ___________

Given 10 and 25 as one of the addends among two addends in their respective addition.

Given numbers 25,10,15,35 are other addends.

Check out placing each addend next to 10.

Equation are ,

10 + 25 = 35

10 + 10 = 20

10 + 15 = 25

10 + 35 =45.

Among this equations, for the first equation is 10 + 15 = 25

and the second is 25 + 10 = 35 because the it fulfills the given condition .(Use each number once to complete the equations.)

Question 16.

**Modeling Real Life**

There are 142 teachers at a school. The school hires 10 more. How many teachers are there now?

_____________ teachers

Answer:

Number of teachers are there now = 152.

Given:

Number of teachers at a school = 142

Number of teachers the school hired more = 10

Explanation:

Number of teachers are there now = Number of teachers at a school + Number of teachers the school hired more

= 142 + 10

= 152.

Hence, Number of teachers are there now = 152.

**Review & Refresh**

Question 17.

10 less than 87 is _________ .

Answer:

87 – 10 = 77.

Explanation:

There are 87 mangoes in a basket.

10 mangoes got spoiled. How many mangoes left??

Subtract the mangoes

87 – 10 = 77.

Hence, equation is 87 – 10 = 77.

Question 18.

1 less than 33 is __________ .

Answer:

33 – 1 = 32

Explanation:

There are 33 mangoes in a basket.

1 mango got spoiled. How many mangoes left??

Subtract the mangoes

33 – 1 = 32.

Hence, equation is 33 – 1 = 32.

### Lesson 8.2 Mental Math: 10 Less

**Explore and Grow**

Find each difference. What do you notice?

33 – 10 = __________

67 – 10 = __________

82 – 10 = __________

Answer:

33 -10 = 23

67 – 10 = 57

82 – 10 = 72

Explanation:

1. The number that is to be subtracted from is called Minuend.

The number that is to be subtracted is called Subtrahend:

The result of subtracting one number from another is called Difference:

In this case, 33 is minuend and 10 is subtrahend.

Now subtract this two:

=> 33 -10 = 23

Hence, difference is 23.

2. In this case, 67 is minuend and 10 is subtrahend.

Now subtract this two:

=> 67 – 10 = 57

Hence, difference is 57.

3. In this case, 82 is minuend and 10 is subtrahend.

Now subtract this two:

=> 82 – 10 = 72

Hence, difference is 72.

**Show and Grow**

Use mental math.

Question 1.

55 – 10 = __________

Answer:

55 – 10 = 45

Explanation:

In this case, 55 is minuend and 10 is subtrahend.

Now subtract this two:

55 – 10 = 45

Hence, Difference = 45.

Question 2.

21 – 10 = __________

Answer:

21 – 10 = 11

Explanation:

In this case, 21 is minuend and 10 is subtrahend.

Now subtract this two:

21 – 10 = 11

Hence, Difference = 11.

Question 3.

18 – 10 = __________

Answer:

18 – 10 =8.

Explanation:

In this case, 18 is minuend and 10 is subtrahend.

Now subtract this two:

18 – 10 =8.

Hence, Difference = 8.

Question 4.

74 – 10 = __________

Answer:

74 – 10 = 64.

Explanation:

In this case, 74 is minuend and 10 is subtrahend.

Now subtract this two:

74 – 10 = 64.

Hence, Difference = 64.

Question 5.

89 – 10 = __________

Answer:

89 – 10 = 79.

Explanation:

In this case, 89 is minuend and 10 is subtrahend.

Now subtract this two:

89 – 10 = 79.

Hence, Difference = 79.

Question 6.

72 – 10 = __________

Answer:

72 – 10 = 62.

Explanation:

In this case, 72 is minuend and 10 is subtrahend.

Now subtract this two:

72 – 10 = 62.

Hence, Difference = 62.

**Apply and Grow: Practice**

Use mental math

Question 7.

60 – 10 = __________

Answer:

60 – 10 = 50.

Explanation:

In this case, 60 is minuend and 10 is subtrahend.

Now subtract this two:

60 – 10 = 50.

Hence, Difference = 50.

Question 8.

45 – 10 = __________

Answer:

45 – 10 = 35

Explanation:

In this case, 45 is minuend and 10 is subtrahend.

Now subtract this two:

45 – 10 = 35

Hence, Difference = 35.

Question 9.

50 – 10 = __________

Answer:

50 – 10 = 40

Explanation:

In this case, 50 is minuend and 10 is subtrahend.

Now subtract this two:

50 – 10 = 40

Hence, Difference = 40.

Question 10.

34 – 10 = __________

Answer:

34 – 10 = 24

Explanation:

In this case, 34 is minuend and 10 is subtrahend.

Now subtract this two:

34 – 10 = 24

Hence, Difference = 24.

Question 11.

51 – 10 = __________

Answer:

51 – 10 = 41

Explanation:

In this case, 51 is minuend and 10 is subtrahend.

Now subtract this two:

51 – 10 = 41

Hence, Difference = 41.

Question 12.

86 – 10 = __________

Answer:

86 – 10 = 76.

Explanation:

In this case, 86 is minuend and 10 is subtrahend.

Now subtract this two:

86 – 10 = 76.

Hence, Difference = 76.

Question 13.

64 – 10 = __________

Answer:

64 – 10 = 54.

Explanation:

In this case, 64 is minuend and 10 is subtrahend.

Now subtract this two:

64 – 10 = 54.

Hence, Difference = 54.

Question 14.

97 – 10 = __________

Answer:

97 – 10 = 87.

Explanation:

In this case, 97 is minuend and 10 is subtrahend.

Now subtract this two:

97 – 10 = 87.

Hence, Difference = 87.

Question 15.

28 – 10 = __________

Answer:

28 – 10 = 18.

Explanation:

In this case, 28 is minuend and 10 is subtrahend.

Now subtract this two:

28 – 10 = 18.

Hence, Difference = 18.

Question 16.

73 – 10 = __________

Answer:

73 – 10 = 63.

Explanation:

In this case, 73 is minuend and 10 is subtrahend.

Now subtract this two:

73 – 10 = 63.

Hence, Difference = 63.

Question 17.

__________ – 10 = 22

Answer:

32 – 10 = 22.

Explanation:

In this case, Missing number is minuend and 10 is subtrahend.

Let missing number be X.

Sum is given = 22

Now subtract:

X – 10 = 80

X = 22 + 10

X = 32.

Hence, Equation = 32 – 10 = 22 .

Question 18.

__________ – 10 = 80

Answer:

90 – 10 = 80.

Explanation:

In this case, Missing number is minuend and 10 is subtrahend.

Let missing number be X.

Sum is given = 80.

Now subtract :

X – 10 = 80

X = 80 + 10

X = 90.

Hence, Equation = 90 – 10 = 80.

Question 19.

**YOU BE THE TEACHER**

Is Newton correct? Explain.

Answer:

94 – 10 = 84.

Explanation:

In this case, 94 is minuend and 10 is subtrahend.

Now subtract this two:

94 – 10 = 84.

Hence, Difference = 84.

Therefore, Newton is correct.

**Think and Grow: Modeling Real Life**

You want to ride all 47 rides at an amusement park. You ride 10 of them. How many rides are left?

Subtraction equation:

_________ rides.

Answer:

Number of rides left = 37.

Given:

Total number of rides you want to ride at an amusement park = 47

Number of rides you have taken out of them = 10

Explanation:

Number of rides left = Total number of rides you want to ride at an amusement park – Number of rides you have taken out of them

= 47 – 10

= 37.

Hence, Number of rides left = 37.

**Show and Grow**

Question 20.

You want to try all 65 flavors at a frozen yogurt shop. You try 10 of them. How many flavors are left?

Subtraction equation:

_________ flavors.

Answer:

Number of flavors left = 55.

Given:

Total number of flavors you want to try at a frozen yogurt shop = 65

Number of flavors you have tried out of them = 10

Explanation:

Number of flavors left = Total number of flavors you want to try at a frozen yogurt shop – Number of flavors you have tried out of them

= 65 – 10

= 55

Hence, Number of flavors left = 55.

### Mental Math: 10 Less Practice 8.2

Use mental math.

Question 1.

12 – 10 = __________

Answer:

12 – 10 = 2.

Explanation:

In this case, 12 is minuend and 10 is subtrahend.

Now subtract this two:

12 – 10 = 2.

Hence, Difference = 2.

Question 2.

49 – 10 = __________

Answer:

49 – 10 = 39.

Explanation:

In this case, 49 is minuend and 10 is subtrahend.

Now subtract this two:

49 – 10 = 39.

Hence, Difference = 39.

Question 3.

37 – 10 = __________

Answer:

37 – 10 = 27.

Explanation:

In this case, 37 is minuend and 10 is subtrahend.

Now subtract this two:

37 – 10 = 27.

Hence, Difference = 27.

Question 4.

26 – 10 = __________

Answer:

26 – 10 = 16.

Explanation:

In this case, 26 is minuend and 10 is subtrahend.

Now subtract this two:

26 – 10 = 16.

Hence, Difference = 16.

Question 5.

40 – 10 = __________

Answer:

40 – 10 = 30.

Explanation:

In this case, 40 is minuend and 10 is subtrahend.

Now subtract this two:

40 – 10 = 30.

Hence, Difference = 30.

Question 6.

62 – 10 = __________

Answer:

62 – 10 = 52.

Explanation:

In this case, 62 is minuend and 10 is subtrahend.

Now subtract this two:

62 – 10 = 52

Hence, Difference = 52.

Question 7.

88 – 10 = __________

Answer:

88 – 10 = 78.

Explanation:

In this case, 88 is minuend and 10 is subtrahend.

Now subtract this two:

88 – 10 = 78.

Hence, Difference =78.

Question 8.

91 – 10 = __________

Answer:

91 – 10 = 81.

Explanation:

In this case, 91 is minuend and 10 is subtrahend.

Now subtract this two:

91 – 10 = 81.

Hence, Difference = 81.

Question 9.

54 – 10 = __________

Answer:

54 – 10 = 44

Explanation:

In this case, 54 is minuend and 10 is subtrahend.

Now subtract this two:

54 – 10 = 44.

Hence, Difference = 44.

Question 10.

76 – 10 = __________

Answer:

76 – 10 = 66.

Explanation:

In this case, 76 is minuend and 10 is subtrahend.

Now subtract this two:

76 – 10 = 66.

Hence, Difference = 66.

Question 11.

__________ – 10 = 15

Answer:

25 – 10 = 15

Explanation:

In this case, Missing number is minuend and 10 is subtrahend.

Let missing number be X.

Sum is given = 15.

Now subtract :

X – 10 = 15

X = 15 + 10

X = 25.

Hence, Equation is 25 – 10 = 15.

Question 12.

__________ – 10 = 77

Answer:

87 – 10 = 77

Explanation:

In this case, Missing number is minuend and 10 is subtrahend.

Let missing number be X.

Sum is given = 77.

Now subtract :

X – 10 = 77

X = 77 + 10

X = 87.

Hence, Equation is 87 – 10 = 77.

Question 13.

__________ – 10 = 34

Answer:

44 – 10 = 34

Explanation:

In this case, Missing number is minuend and 10 is subtrahend.

Let missing number be X.

Sum is given = 34.

Now subtract :

X – 10 = 34

X = 34 + 10

X = 44.

Hence, Equation is 44 – 10 = 34.

Question 14.

__________ – 10 = 53

Answer:

63 – 10 = 53.

Explanation:

In this case, Missing number is minuend and 10 is subtrahend.

Let missing number be X.

Sum is given = 53.

Now subtract :

X – 10 = 53

X = 53 + 10

X = 63.

Hence, Equation is 63 – 10 = 53.

Question 15.

**YOU BE THE TEACHER**

Is Descartes correct? Explain.

Answer:

40 – 10 = 30

Explanation:

In this case, 40 is minuend and 10 is subtrahend.

Now subtract this two:

40 – 10 = 30.

Difference = 30.

Therefore, Descartes answer 50 is incorrect because he did not subtract the numbers instead he added the number.

Question 16.

**Modeling Real Life**

There are 99 levels in a video game. You complete 10 of them. How many are left?

____________ levels

Answer:

Number of games left = 89.

Given:

Total number of levels in a video game = 99

Number of games I have completed out of them = 10

Explanation:

Number of games left = Total number of levels in a video game – Number of games I have completed out of them

= 99 – 10

= 89

Hence, Number of games left = 89.

**Review & Refresh**

Question 17.

A group of students are at the arcade. 4 of them leave. There are 5 left. How many students were there to start?

________ students

Answer:

Total number of students were there to start = 9.

Given:

Number of students leave = 4

Number of students left = 5

Explanation:

Total number of students were there to start = Number of students leave + Number of students left

= 4 + 5

= 9

Hence, total number of students were there to start = 9.

### Lesson 8.3 Add Tens

**Explore and Grow**

Model each problem. How are the problems alike? How are they different?

3 + 2 = _______

30 + 20 = _______

Answer:

3 + 2 = 5.

30 + 20 = 50.

Explanation:

A number that is added to another number is known as an addend.

1. In this case, 3 and 2 are the addends.

Sum is the result of adding two numbers.

3 + 2 = 5.

2. In this case, 30 and 20 are the addends.

Sum is the result of adding two numbers.

30 + 20 = 50.

Hence, the problem is alike in its addition process and different in its sum.

**Show and Grow**

Question 1.

40 + 50 = ?

____________ tens + ____________ tens = ____________ tens

So, 40 + 50 = ____________ .

Answer:

40 + 50 = 90.

Explanation:

Place value is the value of each digit in a number.

4 value in 40 = 4 tens

5 value in 50 = 5 tens

Add the two numbers:

=> 4 tens + 5 tens = 9 tens.

So, 40 + 50 = 90.

Question 2.

30 + 30 = ?

____________ tens + ____________ tens = ____________ tens

So, 30 + 30 = ____________ .

Answer:

30 + 30 = 60.

Explanation:

Place value is the value of each digit in a number.

3 value in 30 = 3 tens

3 value in 30 = 3 tens

Add the two numbers:

3 tens + 3 tens = 6 tens

So, 30 + 30 = 60.

**Apply and Grow: Practice**

Question 3.

20 + 40 = ?

____________ tens + ____________ tens = ____________ tens

So, 20 + 40 = ____________ .

Answer:

20 + 40 = 60

Explanation:

Place value is the value of each digit in a number.

2 value in 20 = 2 tens

4 value in 40 = 4 tens

Add the two numbers:

2 tens + 4 tens = 6 tens

So, 20 + 40 = 60.

Question 4.

50 + 30 = ?

____________ tens + ____________ tens = ____________ tens

So, 50 + 30 = ____________ .

Answer:

50 + 30 = 80.

Explanation:

Place value is the value of each digit in a number.

5 value in 50 = 5 tens

3 value in 30 = 3 tens

Add the two numbers:

5 tens + 3 tens = 8 tens

So, 50 + 30 = 80.

Question 5.

40 + 10 = _________

Answer:

40 + 10 = 50.

Explanation:

Place value is the value of each digit in a number.

4 value in 40 = 4 tens

1 value in 10 = 1 tens

Add the two numbers:

4 tens + 1 tens = 5 tens

So, 40 + 10 = 50.

Question 6.

70 + 20 = _________

Answer:

70 + 20 = 90.

Explanation:

Place value is the value of each digit in a number.

7 value in 70 = 7 tens

2 value in 20 = 2 tens

Add the two numbers:

7 tens + 2 tens = 9 tens

So, 70 + 20 = 90..

Question 7.

30 + 40 = _________

Answer:

30 + 40 = 70.

Explanation:

Place value is the value of each digit in a number.

3 value in 30 = 3 tens

4 value in 40 = 4 tens

Add the two numbers:

3 tens + 4 tens = 7 tens

So, 30 + 40 = 70.

Question 8.

20 + 60 = __________

Answer:

20 + 60 = 80.

Explanation:

Place value is the value of each digit in a number.

2 value in 20 = 2 tens

6 value in 60 = 6 tens

Add the two numbers:

2 tens + 6 tens = 8 tens

So, 20 + 60 = 80.

Question 9.

_________ + 10 = 40

Answer:

30 + 10 = 40.

Explanation:

Let the first addend be X.

Second addend given= 10

Sum is given = 40

Now add :

X + 10 = 40

X = 40 – 10

x = 30.

Hence, Equation is 30 + 10 = 40.

Question 10.

_________ + 60 = 90

Answer:

30 + 60 = 90.

Explanation:

Let the first addend be X.

Second addend given = 60

Sum is given = 90

Now add :

X + 60 = 90

X = 90 – 60

X = 30.

Hence, Equation is 30 + 60 = 90.

Question 11.

**DIG DEEPER!**

Which choices match the model?

50 20 + 30

2 tens + 3 ones 1 ten + 4 tens

Answer:

1 ten + 4 tens = 5 tens.

Explanation:

In the above picture, 5 lines are given.

Considered each line value as 10.

Here, two addends are given in each choice:

Now add this two :

1. 50

2. 20 + 30 = 50

3. 2 tens + 3 ones = 20 + 3=23

4. 1 ten + 4 tens = 5 tens

Hence, 4th choice matches the model because five lines of each value 10 = 50 not others as addition of two numbers it did not refer in the model.

**Think and Grow: Modeling Real Life**

One tray has 20 meatballs. Another tray has the same number of meatballs. How many meatballs are there in all?

Model:

Addition equation:

__________ meatballs

Answer:

Total number of meatballs are there in all = 40.

Given:

Number of meatballs one tray has = 20

Number of meatballs same another tray has = 20

Explanation:

Total number of meatballs are there in all = Number of meatballs one tray has – Number of meatballs same another tray has

= 20 + 20

= 40

Hence, Total number of meatballs are there in all = 40.

**Show and Grow**

Question 12.

One box has 40 bags of pretzels. Another box has the same number of bags. How many bags are there in all?

Model:

Addition equation:

__________ bags

Answer:

Total number of bags are there in all = 80.

Given:

Number of bags of pretzels one box has = 40

Number of bags of pretzels another box has = 40

Explanation:

Total number of bags are there in all = Number of bags of pretzels one box has + Number of bags of pretzels another box has

= 40 + 40

= 80.

Hence, Total number of bags are there in all = 80.

### Add Tens Practice 8.3

Question 1.

20 + 70 = ?

____________ tens + ____________ tens = ____________ tens

So, 20 + 70 = ____________ .

Answer:

2tens + 7tens = 9tens

20 + 70 = 90.

Explanation:

Here place value of 2 and 7 are considered.

Add the two numbers.

2tens + 7tens = 9tens

20 + 70 = 90.

Question 2.

50 + 30 = ?

____________ tens + ____________ tens = ____________ tens

So, 50 + 30 = ____________ .

Answer:

5tens + 3tens = 8tens

50 + 30 = 80.

Explanation:

Here place value of 2 and 7 are considered.

Add the two numbers.

5tens + 3tens = 8tens

50 + 30 = 80.

Question 3.

60 + 20 = ___________

Answer:

6tens + 2tens = 8tens.

60 + 20 = 80.

Explanation:

Here place value of 2 and 7 are considered.

Add the two numbers.

6tens + 2tens = 8tens.

60 + 20 = 80.

Question 4.

40 + 40 = ____________

Answer:

4tens + 4tens = 8tens.

40 + 40 = 80.

Explanation:

Here place value of 4 and 4 are considered.

Add the two numbers.

4tens + 4tens = 8tens.

40 + 40 = 80.

Question 5.

__________ + 40 = 50

Answer:

1 tens + 4 tens = 5 tens.

10 + 40 = 50.

Explanation:

Let the missing number be X.

Add the numbers now.

X + 40 = 50

X = 50 – 40

X = 10

1 tens + 4 tens = 5 tens.

10 + 40 = 50.

Question 6.

___________ + 30 = 60

Answer:

3 tens + 3 tens = 6 tens.

30 + 30 = 60.

Explanation:

Let the missing number be X.

Add the numbers now.

X + 30 = 60

X = 60 – 30

X = 30

3 tens + 3 tens = 6 tens.

30 + 30 = 60.

Question 7.

___________ + 20 = 70

Answer:

5 tens + 2 tens = 7 tens.

50 + 20 = 70.

Explanation:

Let the missing number be X.

Add the numbers now.

X + 20 = 70

X = 70 – 20

X = 50

5 tens + 2 tens = 7 tens.

50 + 20 = 70.

Question 8.

_____________ + 50 = 90

Answer:

5 tens + 4 tens = 90.

50 + 40 = 90.

Explanation:

Let the missing number be X.

Add the numbers now.

X + 50 = 90

X = 90 – 50

X = 40

5 tens + 4 tens = 90.

50 + 40 = 90.

Question 9.

**DIG DEEPER!**

Which choices match the model?

3 tens + 4 ones 5 tens + 2 tens

60 30 + 40

Answer:

3 tens + 4 tens = 7 tens

5 tens + 2 tens = 7 tens

Explanation:

1. 3 tens + 4 tens = 7 tens

2. 60

3. 5 tens + 2 tens = 7 tens

4. 30 + 40 = 70

Hence, 2nd and 3rd choice matches the model because five lines of each value 10 x 7 = 70 not others as addition of two numbers it did not refer in the model.

Question 10.

**Modeling Real Life**

One magic set has 30 pieces. Another set has the same number of pieces. How many pieces are there in all?

_____________ pieces

Answer:

Total Number of pieces are there in all = 60.

Explanation:

Number of pieces magic sets has = 30

Number of pieces another magic sets has same = 30

Total Number of pieces are there in all = Number of pieces magic sets has + Number of pieces another magic sets has same

= 30 + 30

= 60.

Hence, Total Number of pieces are there in all = 60.

**Review & Refresh**

Question 11.

__________ = 6 + 5

Answer:

11 = 6 + 5

Explanation:

Let the sum of addends 6 and 5 be X.

add the two numbers.

X = 6 + 5

X = 11.

Hence, 11 = 6 + 5.

Question 12.

__________ = 3 + 17

Answer:

20 = 3 + 17

Explanation:

Let the sum of addends 3 and 17 be X.

Add the two numbers.

X = 3 + 17

X = 20.

Hence, 20 = 3 + 17.

Question 13.

__________ = 11 + 5

Answer:

16 = 11 + 5.

Explanation:

Let the sum of addends 11 and 5 be X.

Add the two numbers.

X = 11 + 5

X = 16.

Hence, 16 = 11 + 5.

Question 14.

__________ = 5 + 9

Answer:

14 = 5 + 9.

Explanation:

Let the sum of addends 5 and 9 be X.

Add the two numbers.

X = 5 + 9

X = 14.

Hence, 14 = 5 + 9.

### Lesson 8.4 Add Tens Using a Number Line

**Explore and Grow**

Write the missing numbers. How do the hops help you solve?

30 + 20 = _________

Answer:

30 + 20 = 50.

Explanation:

In math, a number line can be defined as a straight line with numbers placed at equal intervals or segments along its length.

Here, in the above picture the interval is calculated and added.

30 + 10 + 10

= 40 + 10

= 50 .

Hence, 30 + 20 = 50.

**Show and Grow**

Question 1.

50 + 40 = __________

Answer:

50 + 40 = 90.

Explanation:

On the number line, give the interval of 10 for 4 times and add them to given number.

Hence, 50 + 40 = 90.

Question 2.

60 + 20 = _____________

Answer:

60 + 20 = 80

Explanation:

On the number line, give the interval of 10 for 2 times and add them to given number.

Hence, 60 + 20 = 80

**Apply and Grow: Practice**

Question 3.

40 + 20 = _________

Answer:

40 + 20 = 60.

Explanation:

On the number line, give the interval of 10 for 2 times and add them to given number.

Hence, 40 + 20 = 60.

Question 4.

50 + 30 = ___________

Answer:

50 + 30 = 80.

Explanation:

On the number line, give the interval of 10 for 3 times and add them to given number.

Hence, 50 + 30 = 80.

Question 5.

60 + 40 = __________

Answer:

60 + 40 = 100.

Explanation:

On the number line, give the interval of 10 for 4 times and add them to given number.

Hence, 60 + 40 = 100.

Question 6.

20 + 50 = ___________

Answer:

20 + 50 = 70.

Explanation:

On the number line, give the interval of 10 for 5 times and add them to given number.

Hence, 20 + 50 = 70.

Question 7.

**MP Structure**

Write an equation that matches the number line.

Answer:

Equation: 70 + 10 +10 = 90.

Explanation:

On the number line, give the interval of 10 for 2 times and add them to given number.

Equation:

70 + 10 +10

= 80 + 10

= 90.

Hence, Equation: 70 + 10 +10 = 90.

**Think and Grow: Modeling Real Life**

You have 20 cans. You collect 20 more cans. Your friend collects 45 cans in all. Who collects more cans?

Model:

Addition equation:

Compare: ___________ ○ ___________

Who collects more cans? You Friend

Answer:

My friend collects 5 more cans than me .

Given:

Number of cans I have = 20

Number of cans I have collected more = 20

Explanation:

Total number of cans I have in all = Number of cans I have + Number of cans I have collected more

20 + 20 = 40.

Total number of cans my friend has = 45

Difference in cans collection = Total number of cans my friend has – Total number of cans I have in all

= 45 – 40

= 5

Comparison:

Hence, my friend collects 5 more cans than me .

**Show and Grow**

Question 8.

Your class makes 62 paper airplanes. Your friend’s class makes 30 small airplanes and 30 large airplanes. Whose class makes more airplanes?

Model:

Addition equation:

Compare: ___________ ○ ___________

Whose class makes more airplanes?

Your class Friend’s class

Answer:

Total number of paper airplanes I make are 2 more than my friends paper making airplanes.

Given:

Total number of paper airplanes I make = 62

Number of paper small airplanes my friend’s class makes = 30

Number of paper large airplanes my friend’s class makes = 30

Explanation:

Total number of airplanes my friend’s class makes = Number of paper small airplanes my friend’s class makes + Number of paper large airplanes my friend’s class makes

= 30 + 30

= 60

Number of airplanes who makes more = Total number of paper airplanes class I makes – Total number of airplanes my friend’s class makes

=62 – 60

= 2

Comparison:

Hence, Total number of paper airplanes I make 2 more than my friends paper making airplanes.

### Add Tens Using a Number Line Practice 8.4

Question 1.

60 + 30 = __________

Answer:

60 + 30 = 90.

Explanation:

Equation:

60+ 10 +10 +10

=70 + 10 +10

= 80 + 10

=90.

Question 2.

20 + 20 = __________

Answer:

20 + 10+ 10 = 40.

Explanation:

Equation:

20 + 10+ 10

= 30 + 10

= 40.

Question 3.

30 + 70 = __________

Answer:

30 + 70 = 100.

Explanation:

Equation:

30 + 10 + 10+ 10+ 10+ 10+ 10 +10

= 40 + 10+ 10+ 10+ 10+ 10 +10

= 50 +10+ 10+ 10+ 10 +10

= 60 +10+ 10+ 10 +10

= 70 + 10 + 10 +10

= 80 + 10 +10

= 90 + 10

= 100.

Question 4.

**MP Structure**

Write an equation that matches the number line.

Answer:

Equation:

10 + 40 = 50.

Explanation:

The number line shows the interval of 10 for 4 times.

10 + 10 + 10 + 10 +10

= 20 + 10 + 10 + 10

= 30 + 10 + 10

= 40 + 10

= 50.

Question 5.

**Modeling Real Life**

You make 3 snow bricks. Your friend makes 20 small snow bricks and 30 large snow bricks. Who makes more snow bricks?

Who makes more snow bricks? You Friend

Answer:

My friend has 47 more snow bricks than me.

Given:

Total number of snow bricks I have made = 3

Number of small snow bricks my friend has made = 20

Number of large snow bricks my friend has made = 30

Explanation:

Total number of small and large snow bricks my friend has made = Number of small snow bricks my friend has made + Number of large snow bricks my friend has made

= 20 + 30

= 50

Number of snow bricks who makes more = Total number of small and large snow bricks my friend has made – total number of snow bricks I have made

= 50 – 3

= 47.

Comparison:

Hence, my friend has 47 more snow bricks than me.

**Review & Refresh**

Question 6.

Get to lo to subtract.

17 – 8 = ?

17 – __________ = 10

10 – __________ = __________

So, 17 – 8 = __________ .

Answer:

17 – 8 = 9.

Given:

1. 17 – ____ = 10

Let the missing subtrahend be X.

Difference is given = 10

Subtract the numbers.

17 – X = 10

17 = 10 + X

17 – 10 = X

7 = X

Equation: 17 – 7 = 10.

### Lesson 8.5 Subtract Tens

**Explore and Grow**

Model each problem. How are the problems alike? How are they different?

5 – 2 = ___________

50 – 20 = ___________

Answer:

5 – 2 = 3.

50 – 20 = 30.

Explanation:

Here, the minuend is 5 and the subtrahend is 2.**
**Now, Subtract the two numbers.

5 – 2 = 3.

Here, the minuend is 50 and the subtrahend is 20.

**Now, Subtract the two numbers.**

50 – 20 = 30.

Hence, the two equations are alike in the subtraction process yet different in the answers.

**Show and Grow**

Question 1.

70 – 30 = ?

____________ tens – ____________ tens = ____________ tens

So, 70 – 30 = ____________ .

Answer:

7 tens – 3 tens = 4 tens

70 – 30 = 40.

Explanation:

Place value is the value of each digit in a number.

7 value in 70 =7 tens

3 value in 30 = 3 tens

Subtract the two numbers:

7 tens – 3 tens = 4 tens

So, 70 – 30 = 40.

Question 2.

40 – 20 = __________

____________ tens – ____________ tens = ____________ tens

So, 40 – 20 = ____________ .

Answer:

4 tens – 2 tens = 2 tens.

40 – 20 = 20.

Explanation:

Place value is the value of each digit in a number.

4 value in 40 =4 tens

2 value in 20 = 2 tens

Subtract the two numbers:

4 tens – 2 tens = 2 tens.

So, 40 – 20 = 20.

**Apply and Grow: Practice**

Question 3.

90 – 30 = ?

____________ tens – ____________ tens = ____________ tens

So, 90 – 30 = ____________ .

Answer:

9 tens – 3 tens = 6 tens.

90 – 30 = 60.

Explanation:

Place value is the value of each digit in a number.

9 value in 90 =9 tens

3 value in 30 = 3 tens

Subtract the two numbers:

9 tens – 3 tens = 6 tens.

So, 90 – 30 = 60.

Question 4.

50 – 10 = ?

____________ tens – ____________ tens = ____________ tens

So, 50 – 10 = ____________ .

Answer:

5 tens – 1 tens = 4 tens.

50 – 10 = 40.

Explanation:

Place value is the value of each digit in a number.

5 value in 50 = 5 tens

1 value in 10 = 1 tens

Subtract the two numbers:

5 tens – 1 tens = 4 tens.

So, 50 – 10 = 40.

Question 5.

30 – 20 = __________

Answer:

30 – 20 = 10.

Explanation:

Place value is the value of each digit in a number.

3 value in 30 = 5 tens

2 value in 20 = 2 tens

Subtract the two numbers:

3 tens – 2 tens = 1 tens.

So, 30 – 20 = 10.

Question 6.

40 – 40 = __________

Answer:

40 – 40 = 0.

Explanation:

Place value is the value of each digit in a number.

4 value in 40 = 4 tens

4 value in 40 = 4 tens

Subtract the two numbers:

4 tens – 4 tens = 0 tens.

So, 40 – 40 = 0.

Question 7.

80 – 50 = __________

Answer:

80 – 50 = 30.

Explanation:

Place value is the value of each digit in a number.

8 value in 80 = 8 tens

5 value in 50 = 5 tens

Subtract the two numbers:

8 tens – 5 tens = 3 tens.

So, 80 – 50 = 30.

Question 8.

90 – 70 = ___________

Answer:

90 – 70 = 20.

Explanation:

Place value is the value of each digit in a number.

9 value in 90 = 9 tens

7 value in 70 = 7 tens

Subtract the two numbers:

9 tens – 7 tens = 2 tens.

So, 90 – 70 = 20.

Question 9.

20 – __________ = 10

Answer:

20 – 10 = 10.

Explanation:

Here, the minuend is 20.

Difference is 10.

Let the subtrahend be X.

Now, subtract the numbers.

20 – X = 10.

20 = 10 + X

20 – 10 = X

10 = X.

Hence, 20 – 10 = 10.

Question 10.

50 – __________ = 20

Answer:

50 – 30 = 20.

Explanation:

Here, the minuend is 50.

Difference is 20.

Let the subtrahend be X.

Now, subtract the numbers.

50 – X = 20.

50 = 20 + X

50 – 20 = X

30 = X.

Hence, 50 – 30 = 20.

Question 11.

**DIG DEEPER!**

Which choices match the model?

50 – 30 80 – 30

5 tens – 3 tens 8 tens – 3 tens

Answer:

8 tens – 3 tens = 5 tens.

Explanation:

In the given picture, total there are eight lines.

Consider each line value is 10. Out of them 3 lines are removed.

=> 80 – 30 = 50.

2. 50 – 30 = 20

3. 5 tens – 3 tens = 2 tens.

4. 8 tens – 3 tens = 5 tens.

Hence, 4th equation is suitable for the model .

**Think and Grow: Modeling Real Life**

You have 80 math problems. You have 40 fewer spelling words. How many spelling words do you have?

Model:

Subtraction equation:

______________ spelling words

Answer:

Number of spelling words I have = 40.

Explanation:

Total number of math problems I have = 80

Number of fewer spelling words = 40

Subtraction equation:

Number of spelling words do you have = Total number of math problems I have – Number of fewer spelling words

= 80 – 40

= 40.

Hence, Number of spelling words I have = 40.

**Show and Grow**

Question 12.

There are 60 students in a play. A football team has 30 fewer students. How many students are on the football team?

Model:

Subtraction equation:

______________ students

Answer:

Number of students on the football team = 30.

Explanation:

Total number of students in a play = 60

Number of fewer students in a football team = 30

Subtraction equation:

Number of students on the football team = Total number of students in a play – Number of fewer students in a football team

= 60 – 30

= 30

Hence, Number of students on the football team = 30.

### Subtract Tens Practice 8.5

Question 1.

70 – 50 = ?

____________ tens – ____________ tens = ____________ tens

So, 70 – 50 = ____________ .

Answer:

70 – 50 = 20.

7 tens – 5 tens = 2 tens.

Explanation:

Place value is the value of each digit in a number.

7 value in 70 = 7 tens

5 value in 50 = 5 tens

Subtract the two numbers:

7 tens – 5 tens = 2 tens.

So, 70 – 50 = 20.

Question 2.

60 – 20 = ?

____________ tens – ____________ tens = ____________ tens

So, 60 – 20 = ____________ .

Answer:

60 – 20 = 40.

6 tens – 2 tens = 4 tens.

Explanation:

Place value is the value of each digit in a number.

6 value in 60 = 6 tens

2 value in 20 = 2 tens

Subtract the two numbers:

6 tens – 2 tens = 4 tens.

So, 60 – 20 = 40.

Question 3.

60 – 60 = __________

Answer:

60 – 60 = 0.

Explanation:

Here, the minuend is 60 and subtrahend is 60.

Subtract the two numbers:

60 – 60 = 0.

Question 4.

30 – 10 = ____________

Answer:

30 – 10 = 20.

Explanation:

Here, the minuend is 30 and subtrahend is 10.

Subtract the two numbers:

30 – 10 = 20.

Question 5.

70 – __________ = 0

Answer:

70 – 70 =0.

Explanation:

Here, the minuend is 70.

Let the subtrahend be X

Difference = 0.

Subtract the two numbers:

70 – X = 0

70 = 0 + X

70 – 0 = X

70 = X

Equation is 70 – 70 =0.

Question 6.

50 – ___________ = 40

Answer:

50 – 10 =40.

Explanation:

Here, the minuend is 50.

Let the subtrahend be X

Difference = 40.

Subtract the two numbers:

50 – X = 40

50 = 40 + X

50 – 40 = X

10 = X

Equation is 50 – 10 =40.

Question 7.

40 – ____________ = 20

Answer:

40 – 20 = 20.

Explanation:

Here, the minuend is 40.

Let the subtrahend be X

Difference = 20.

Subtract the two numbers:

40 – X = 20

40 = 20 + X

40 – 20 = X

20 = X

Equation is 40 – 20 = 20.

Question 8.

90 – ____________ = 50

Answer:

90 – 40 =50.

Explanation:

Here, the minuend is 90.

Let the subtrahend be X

Difference = 50.

Subtract the two numbers:

90 – X = 50

90 = 50 + X

90 – 50 = X

40 = X

Equation is 90 – 40 =50.

Question 9.

**DIG DEEPER!**

Which choices match the model?

9o – 50 40 – 50

4 tens – 5 ones 9 tens – 5 tens

Answer:

9 tens – 5 tens = 4 tens.

Explanation:

In the given picture, total there are nine lines.

Consider each line value is 10. Out of them 5 lines are removed.

=> 9 tens – 5 tens = 4 tens

2. 90 – 50 = 40

3. 40 – 50 = -10

4. 4 tens – 5 ones = 40 + 5 = 45.

Hence, out of four choices, the first choice is correct for the model than other three equations.

Question 10.

**Modeling Real Life**

There are 40 chairs in the library. There are 30 fewer tables than chairs. How many tables are there?

___________ tables

Answer:

Number of tables are there = 10.

Explanation:

Total number of chairs in a library = 40

Number of fewer tables than chairs = 30

Number of tables are there = Total number of chairs in a library – Number of fewer tables than chairs

= 40 – 30

= 10.

Hence, Number of tables are there = 10.

**Review & Refresh**

Question 11.

11 – 7 = ____________

Answer:

11 – 7 = 4

Explanation:

Here, the minuend is 17 and subtrahend is 7.

Subtract the two numbers:

11 – 7 = 4

Hence, 11 – 7 = 4.

Question 12.

16 – 8 = ____________

Answer:

16 – 8 = 8.

Explanation:

Here, the minuend is 16 and subtrahend is 8.

Subtract the two numbers:

16 – 8 = 8.

Hence, 16 – 8 = 8.

Question 13.

15 – 8 = ____________

Answer:

15 – 8 = 7.

Explanation:

Here, the minuend is 15 and subtrahend is 8.

Subtract the two numbers:

15 – 8 = 7.

Hence, 15 – 8 = 7.

Question 14.

18 – 9 = ____________

Answer:

18 – 9 = 9.

Explanation:

Here, the minuend is 18 and subtrahend is 9.

Subtract the two numbers:

18 – 9 = 9.

Hence, 18 – 9 = 9.

### Lesson 8.6 Subtract Tens Using a Number Line

**Explore and Grow**

Write the missing numbers. How do the hops help you solve?

40 – 20 = ___________

Answer:

40 – 20 = 20.

Explanation:

In math, a number line can be defined as a straight line with numbers placed at equal intervals or segments along its length.

Here, we need to represent 20 subtracted from 40.

**Show and Grow**

Question 1.

80 – 50 = __________

Answer:

80 – 50 = 30.

Explanation:

Here, we need to represent 50 subtracted from 80.

Question 2.

70 – 30 = ___________

Answer:

70 – 30 = 40.

Explanation:

Here, we need to represent 30 subtracted from 70.

**Apply and Grow: Practice**

Question 3.

60 – 20 = __________

Answer:

60 – 20 = 40.

Explanation:

Here, we need to represent 20 subtracted from 60.

Question 4.

40 – 30 = ____________

Answer:

40 – 30 = 10.

Explanation:

Here, we need to represent 30 subtracted from 40.

Question 5.

90 – 40 = ____________

Answer:

90 – 40 = 50.

Explanation:

Here, we need to represent 40 subtracted from 90.

Question 6.

90 – 70 = ____________

Answer:

90 – 70 = 20.

Explanation:

Here, we need to represent 70 subtracted from 90.

Question 7.

**MP Structure**

Write the equation that matches the number line.

Answer:

80 – 40 = 40

Explanation:

80 – 10 -10 – 10 -10

= 70 -10 – 10 -10

= 60 – 10 -10

= 50 -10

= 40.

**Think and Grow: Modeling Real Life**

You have a bucket of 80 golf balls. You hit 60 of them. Your friend has 28 golf balls left. Who has more golf balls left?

Model:

Subtraction equation:

Compare: __________ ○ ___________

Who has more golf balls left? You Friend

Answer:

My friend has left 8 golf balls more than me.

Given:

Total number of golf balls I have = 80

Number of golf balls I hit out of them = 60

Explanation:

Number of gold balls I left = Total number of golf balls I have – Number of golf balls I hit out of them

= 80 – 60

= 20

Number of golf balls my friend left = 28

Comparison:

Number of golf balls who left more = Number of golf balls my friend left – Number of gold balls I left

= 28 – 20

= 8.

Hence, my friend has left 8 golf balls more than me.

**Show and Grow**

Question 8.

Pack A has 50 batteries. 40 of them have been used. Pack B has 15 batteries. Which pack has more bafferies left?

Model:

Subtraction equation:

Compare: __________ ○ ___________

Who has more golf balls left? Pack A Pack B

Answer:

5 batteries are left more in pack B than pack A.

Given:

Total number of batteries in pack A has= 50

Number of batteries used in pack A = 40

Total number of batteries in pack B has = 15

Explanation:

Number of batteries left in pack A = Total number of batteries in pack A has – Number of batteries used in pack A

= 50 – 40

= 10.

Comparison:

Number of batteries which pack has left more = Total number of batteries in pack B has – Number of batteries left in pack A

= 15 – 10

= 5

Hence,5 batteries are left more in pack B than pack A.

### Subtract Tens Using a Number Line Practice 8.6

Question 1.

50 – 30 = _____________

Answer:

50 – 30 = 20.

Explanation:

Here, we need to represent 30 subtracted from 50.

Question 2.

80 – 60 = ____________

Answer:

80 – 60 = 20.

Explanation:

Here, we need to represent 60 subtracted from 80.

Question 3.

90 – 20 = ____________

Answer:

90 – 20 = 70.

Explanation:

Here, we need to represent 20 subtracted from 90.

Question 4.

**MP Structure**

Write the equation that matches the number line.

Answer:

60 – 50 = 10.

Explanation:

Here we need to subtract 10 5times from 60.

60 – 10 -10 -10 -10 -10

= 50 -10 -10 -10 -10

= 40 – 10 -10 -10

= 30 – 10 -10

= 20 – 10

= 10.

Question 5.

**Modeling Real Life**

You have 80 raffle tickets and give away 30 of them. Your friend has 47 raffle tickets. Who has more raffle tickets?

Who has more raffle tickets? You Friend

Answer:

I have 5 raffle tickets more than my friend.

Given:

Total number of raffle tickets = 80

Number of raffle tickets I gave away = 30

Explanation:

Number of raffle tickets I have now = Total number of raffle tickets – Number of raffle tickets I gave away

= 80 -30

= 50

Number of raffles tickets my friend has = 47

Comparison:

Number of raffle ticket who has more = Number of raffle tickets I have now – Number of raffles tickets my friend has

= 50 – 47

= 3

Hence, I have 5 raffle tickets more than my friend.

**Review & Refresh**

Question 6.

13 – 8 = ?

Think 8 + __________ = 13.

So, 13 – 8 = __________ .

Answer:

13 – 8 = 5.

Explanation:

Think 8 + ____5______ = 13.

So, 13 – 8 = ___5_______ .

Question 7.

15 – 7 = ?

Think 7 + _________ = 15

So, 15 – 7 = ____________ .

Answer:

15 – 7 = 8.

Explanation:

Think 7 + ____8_____ = 15

So, 15 – 7 = ______8______ .

### Lesson 8.7 Use Addition to Subtract Tens

**Explore and Grow**

Complete each equation. What do you notice?

Answer:

20 + 50 = 70

50 – 20 = 30.

Explanation:

Here, for number 20 we are adding 5 times 10.

Here, we are subtracting 20 from number 50.

**Show and Grow**

Question 1.

90 – 70 = ?

Think 70 + _________ = 90

So, 90 – 70 = _________ .

Answer:

90 – 70 = 20.

Explanation:

Think 70 + ____20_____ = 90

So, 90 – 70 = ___20______ .

Question 2.

60 – 30 = ?

Think 30 + _________ = 60

So, 60 – 30 = _________ .

Answer:

60 – 30 = 30.

Explanation:

Think 30 + __30___ = 60

So, 60 – 30 =____30___.

**Apply and Grow: Practice**

Question 3.

50 – 30 = ?

Think 30 + _________ = 50

So, 50 – 30 = _________ .

Answer:

50 – 30 = 20.

Explanation:

Think 30 + __20_______ = 50

So, 50 – 30 = ___20______ .

Question 4.

70 – 20 = ?

Think 20 + _________ = 70

So, 70 – 20 = _________ .

Answer:

70 – 20 = 50.

Explanation:

Think 20 + ____50_____ = 70

So, 70 – 20 = __50_______ .

Question 5.

90 – 50 = ?

Think 50 + _________ = 90

So, 90 – 50 = _________ .

Answer:

90 – 50 = 40.

Explanation:

Think 50 + _____40____ = 90

So, 90 – 50 = _____40____ .

Question 6.

**MP Structure**

Match the related addition and subtraction equations.

60 + 10 = 70 70 – 50 = 20

50 + 10 = 60 70 – 60 = 10

50 + 20 = 70 60 – 50 = 10

Answer:

Explanation:

60 + 10 = 70 and 70 – 60 = 10 are related addition and subtraction equations because both deals with 60, 10 and 70.

50 + 10 = 60 and 60 – 50 = 10 are related addition and subtraction equations because both deals with 60, 10 and 50.

50 + 20 = 70 and 70 – 50 = 20 are related addition and subtraction equations because both deals with 70, 20 and 50.

**Think and Grow: Modeling Real Life**

A dentist has 40 toothbrushes. She gives away 20 of them. How many toothbrushes does she have left?

Model:

Subtraction equation:

______________ toothbrushes

Answer:

Number of tooth brushes left = 20.

Explanation:

Total number of tooth brushes a dentist has = 40

Number of tooth brushes gave away = 20

Number of tooth brushes left = Total number of tooth brushes a dentist has – Number of tooth brushes gave away

= 40 – 20

= 20

Hence, Number of tooth brushes left = 20.

**Show and Grow**

Question 7.

An art room has 70 bottles of glitter. 30 have been used. How many bottles are left?

Model:

Subtraction equation:

______________ bottles

Answer:

Number of bottles of glitter left = 40.

Explanation:

Total number bottles of glitter in an art room = 70

Number of bottles of glitter used = 30

Number of bottles of glitter left = Total number bottles of glitter in an art room – Number of bottles of glitter used

= 70 – 30

= 40.

Hence, Number of bottles of glitter left = 40.

### Use Addition to Subtract Tens Practice 8.7

Question 1.

70 – 40 = ?

Think 40 + __________ = 70

So, 70 – 40 = _________ .

Answer:

70 – 40 = 30.

Explanation:

Think 40 + ____30______ = 70

So, 70 – 40 = ___30______ .

Question 2.

90 – 30 = ?

Think 60 + __________ = 90

So, 90 – 30 = _________ .

Answer:

90 – 30 = 60.

Explanation:

Think 60 + _____30_____ = 90

So, 90 – 30 = ____60_____ .

Question 3.

**MP Structure**

Match the related addition and subtraction equations.

30 + 10 = 40 50 – 40 = 10

40 + 10 = 50 50 – 30 = 20

30 + 20 = 50 40 – 30 = 10

Answer:

Explanation:

30 + 10 = 40 and 40 – 30 = 10 are related addition and subtraction equations because both deals with 40, 10 and 30.

40 + 10 = 50 and 50 – 40 = 10 are related addition and subtraction equations because both deals with 40, 10 and 50.

30 + 20 = 50 and 50 – 30 = 20 are related addition and subtraction equations because both deals with 30, 20 and 50.

Question 4.

**Modeling Real Life**

Newton has 80 newspapers to deliver. He delivers 50 of them. How many newspapers does he have left?

______________ newspapers

Answer:

Number of newspapers left = 30.

Explanation:

Total number of newspapers to deliver = 80

Number of newspapers delivered = 50

Number of newspapers left = Total number of newspapers to deliver – Number of newspapers delivered

= 80 – 50

= 30.

Hence, Number of newspapers left = 30.

**Review & Refresh**

Question 5.

Make quick sketches to compare the numbers.

Answer:

43 > 34.

34 < 43.

Explanation:

43 is greater than 34.

34 is lesser than 43.

### Lesson 8.8 Add Tens to a Number

**Explore and Grow**

15 + 10 = ________ 27 + 10 = __________

15 + 20 = ________ 27 + 20 = __________

15 + 30 = ________ 27 + 30 = __________

Answer:

15 + 10 = ___25_____ 27 + 10 = ___37_______

15 + 20 = ___35_____ 27 + 20 = ____47______

15 + 30 = _____45___ 27 + 30 = ___57_______

Explanation:

**Show and Grow**

Question 1.

23 + 50 = ____________

Answer:

23 + 50 = 73.

Question 2.

6 + 70 = ____________

Answer:

6 + 70 = 76.

**Apply and Grow: practice**

Question 3.

27 + 40 = ____________

Answer:

27 + 40 = 67.

Question 4.

8 + 80 = ____________

Answer:

8 + 80 = 88.

Question 5.

60 + 35 = ____________

Answer:

60 + 35 = 95.

Question 6.

30 + 44 = ____________

Answer:

30 + 44 = 74.

Question 7.

____________ = 33 + 20

Answer:

53 = 33 + 20.

Question 8.

____________ = 70 + 22

Answer:

92= 70 + 22.

Question 9.

**YOU BE THE TEACHER**

Is Newton correct? Explain.

Answer:

36 +50 = 86.

Newton is correct.

Explanation:

36 +50 = 86.

Hence, Newton is correct because the addition of both the addends is correct.

**Think and Grow: Modeling Real Life**

You count 8 birds on your way to school. You count 40 more on your way home. Your friend counts 45 birds in all. Who counts more birds?

Model:

Addition equation:

Compare: ___________ ○ ____________

Who counts more birds? You Friend

Answer:

I have counted 3 birds more than my friend.

Explanation:

Number of birds I counted on the way to school = 8

Number of birds I counted more on your way home = 40

Total number of birds my friend counts in all = 45

Total number of birds I counted in all = Number of birds I counted on the way to school – Number of birds I counted more on your way home

= 8 + 40

= 48.

Comparison:

Number of birds who counted more = Total number of birds I counted in all – Total number of birds my friend counts in all

= 48 – 45

= 3

Hence, I have counted 3 birds more than my friend.

**Show and Grow**

Question 10.

You make 21 snowballs. Your friend makes 11 small snowballs and 20 large snowballs. Who makes more snowballs?

Model:

Addition equation:

Compare: ___________ ○ ____________

Who counts more birds? You Friend

Answer:

Number of snow balls who made more = 10.

Explanation:

Total number of snow balls I made = 21

Total number of small snow balls my friend made =11

Total number of large snow balls my friend made = 20

Total number of snow balls my friend made = Total number of small snow balls my friend made + Total number of large snow balls my friend made

= 11 + 20

= 31

Comparison:

Number of snow balls who made more = Total number of snow balls my friend made – Total number of snow balls I made

= 31 – 21

= 10.

Hence, the Number of snow balls who made more = 10.

### Add Tens to a Number Practice 8.8

Question 1.

19 + 40 = __________

Answer:

19 + 40 = 59.

Question 2.

60 + 23 = __________

Answer:

60 + 23 = 83.

Question 3.

__________ = 5 + 90

Answer:

95 = 5 + 90.

Question 4.

__________ = 37 + 30

Answer:

67 = 37 + 30.

Question 5.

**YOU BE THE TEACHER**

Is Descartes correct? Explain.

Answer:

Descartes is incorrect.

Explanation:

46 + 20 = 66.

Hence, Descartes is incorrect because he did not do the addition correctly.

Question 6.

**Modeling Real Life**

You have 24 glow sticks and buy 40 more. Your friend has 66 glow sticks. Who has more glow sticks?

Who has more glow sticks? You Friend

Answer:

My friend has 2 glow sticks more than me.

Explanation:

Number of glow sticks I have = 24

Number of glow sticks I have purchased more = 40

Total number of glow sticks I have = Number of glow sticks I have + Number of glow sticks I have purchased more

= 24 + 40

= 64

Number of glow sticks my friend has = 66

Comparison:

Number of glow sticks who has more = Number of glow sticks my friend has – Total number of glow sticks I have

= 66 – 64

= 2

Hence, my friend has 2 glow sticks more than me.

**Review & Refresh**

Question 7.

Circle the solid shapes that stack.

Answer:

Explanation:

In Geometry, Solids are three-dimensional shapes because they have three dimensions such as length, breadth and height. The bodies which occupy space are called solids.

here in the above picture, cone , cylinder ,cube are solid shapes that stack not sphere shape ball.

### Add and Subtract Tens Performance Task

Question 1.

The tables show the numbers of seconds 3 pinwheels and 3 fops spin.

a. How many more seconds does the yellow top spin than the red pinwheel?

__________ seconds

Answer:

Number of more seconds the yellow top spin than the red pinwheel taken = 50.

Explanation:

Number of seconds red pinwheel taken = 40

Number of seconds yellow pinwheel taken = 90

Number of more seconds the yellow top spin than the red pinwheel taken = Number of seconds red pinwheel taken – Number of seconds yellow pinwheel taken

= 90 – 40

= 50.

Hence, Number of more seconds the yellow top spin than the red pinwheel taken = 50.

b. The red pinwheel spins 30 fewer seconds than the red top. How long does the red top spin?

__________ seconds

Answer:

The number of seconds the red top taken = 70.

Explanation:

Number of seconds the red pinwheels spins = 40

Let the number of seconds the red top taken be X

The number of seconds the red top taken – 30 = Number of seconds the red pinwheels spins

(The red pinwheel spins 30 fewer seconds than the red top)

=> X – 30 = 40

=> X = 40 + 30

=> X = 70

Hence, The number of seconds the red top taken = 70.

c. The blue pinwheel and the blue top spin for 96 seconds in all. How long does the blue pinwheel spin?

__________ seconds

Answer:

Number of seconds blue pinwheel spin taken = 60.

Explanation:

Number of seconds blue top spin taken = 36

Total number of seconds the blue pinwheel and the blue top spins = 96

Number of seconds blue pinwheel spin taken = Number of seconds blue top spin taken – Total number of seconds the blue pinwheel and the blue top spins

= 96 – 36

= 60.

Hence, Number of seconds blue pinwheel spin taken = 60.

d. Which pinwheel spins the longest?

Red Yellow Blue

Answer:

The yellow pinwheel spins the longest than other pinwheels.

Explanation:

Number of seconds blue pinwheel spin taken = 60

Number of seconds yellow pinwheel spin taken = 90

Number of seconds red pinwheel spin taken = 40

Among, the three pinwheels, the yellow pinwheel spins the longest than other pinwheels.

### Add and Subtract Tens Chapter Practice

### Mental Math: 10 More Homework & Practice 8.1

Use mental math.

Question 1.

58 + 10 = ___________

Answer:

58 + 10 = 68.

Question 2.

15 + 10 = ___________

Answer:

15 + 10 = 25.

Question 3.

29 + 10 = ___________

Answer:

29 + 10 = 39.

Question 4.

41 + 10 = ___________

Answer:

41 + 10 = 51.

Question 5.

10 + 7 = ___________

Answer:

10 + 7 = 17.

Question 6.

10 + 36 = ___________

Answer:

10 + 36 = 46.

Question 7.

84 + ___________ = 94

Answer:

84 + 10= 94

Explanation:

Let the missing number be X.

Add the addends.

84 + X = 94

X = 94 – 84

X = 10.

Question 8.

47 + ___________ = 57

Answer:

47 + 10 = 57.

Explanation:

Let the missing number be X.

add the addends.

47 + X = 57

X = 57 – 47

X =10.

### Mental Math: 10 Less Homework & Practice 8.2

Use mental math.

Question 9.

24 – 10 = ___________

Answer:

24 – 10 = 14.

Question 10.

78 – 10 = ___________

Answer:

78 – 10 = 68.

Question 11.

31 – 10 = ___________

Answer:

31 – 10 = 21.

Question 12.

95 – 10 = ___________

Answer:

95 – 10 = 85.

Question 13.

___________ – 10 = 7

Answer:

17 – 10 = 7.

Explanation:

Let the Missing minuend be X.

Subtrahend = 10

Difference = 7

Subtract the numbers:

X – 10 = 7

X = 7 + 10

X = 17.

Hence, 17 – 10 = 7.

Question 14.

___________ – 10 = 43

Answer:

53 – 10 = 43.

Explanation:

Let the Missing minuend be X.

Subtrahend = 10

Difference = 43

Subtract the numbers:

X – 10 = 43

X = 43 + 10

X = 53.

Hence, 53 – 10 = 43.

### Add Tens Homework & Practice 8.3

Question 15.

60 + 20 = ?

__________ tens + ___________ tens = ___________ tens

So, 60 + 20 = ___________ .

Answer:

60 + 20 = 80.

Explanation:

_______6___ tens + _______2____ tens = ______8_____ tens

So, 60 + 20 = _____80______ .

Question 16.

30 + 50 = ___________

Answer:

30 + 50 = 80.

Question 17.

___________ + 30 = 90

Answer:

60 + 30 = 90.

Explanation:

Let the missing addend be X.

sum = 90

Add the numbers

X + 30= 90

X = 90 – 30

X = 60.

Hence, 60 + 30 = 90.

### Add Tens Using a Number Line Homework & Practice 8.4

Question 18.

50 + 40 = ___________

Answer:

50 + 40 = 90.

Explanation:

Question 19.

**MP Structure**

Write an equation that matches the number line.

Answer:

Equation:

20 + 30 =50.

Explanation:

20 + 10 +10 +10

= 30 +10 +10

= 40 + 10

= 50.

### Subtract Tens Homework & Practice 8.5

Question 20.

90 – 40 = ?

__________ tens – ___________ tens = ___________ tens

So, 90 – 40 = ___________ .

Answer:

90 – 40 = 50.

Explanation:

___9__tens – __4_____ tens = ______5_____ tens

So, 90 – 40 = _50__________ .

Question 21.

70 – 40 = ___________

Answer:

70 – 40 = 20.

Question 22.

80 – __________ = 60

Answer:

80 – 20 = 60.

Explanation:

Let the missing number be X.

Add the addends.

80 – X = 60

80 = 60 + X

80 – 60 = X

20 = X.

### Subtract Tens Using a Number Line Homework & Practice 8.6

Question 23.

60 – 40 = __________

Answer:

60 – 40 = 20.

Explanation:

Question 24.

**MP Structure**

Write the equation that matches the number line.

Answer:

Equation: 70 – 20 = 50.

Explanation:

Number line representation :

70 – 10 -10

= 60 -10

= 50.

### Use Addition to Subtract Tens Homework & Practice 8.7

Question 25.

80 – 60 = ?

Think 60 + __________ = 80

So, 80 – 60 = __________ .

Answer:

80 – 60 = 20.

Explanation:

Think 60 + ____20______ = 80

So, 80 – 60 = _____20_____ .

Question 26.

**Modeling Real Life**

A mail carrier has 90 packages to deliver. She delivers 60 of them. How many packages are left?

______________ packages

Answer:

Number of packages left = 30.

Explanation:

Number of packages are there for deliver = 90

number of packages she delivered = 60

Number of packages left = Number of packages are there for deliver – number of packages she delivered

= 90 – 60

= 30.

Hence, Number of packages left = 30.

### Add Tens to a Number Homework & Practice 8.8

Question 27.

27 + 50 = ____________

Answer:

27 + 50 = 77.

Question 28.

_____________ = 80 + 12

Answer:

92 = 80 + 12.

*Conclusion:*

You can know how to use the number line in a simple method from our Big Ideas Math Book 1st Grade Answer Key Chapter 8 Add and Subtract Tens. Learn the fundamentals of maths like addition and subtraction from this page. Bookmark our page to get the Answer Key of all Big Ideas Math Grade 1 Chapters from 1 to 14.