All the solutions provided in **McGraw Hill Math Grade 3 Answer Key PDF Chapter 8 Lesson 2 Multiply by 7** will give you a clear idea of the concepts.

## McGraw-Hill My Math Grade 3 Answer Key Chapter 8 Lesson 2 Multiply by 7

**Math in My World**

Example 1

A museum has a display of 9 kinds of beetles. There are 7 of each kind of beetle. How many beetles are on display? Write a multiplication sentence with a symbol for the unknown.

9 × 7 = .

Decompose the factor 7 into addends of 5 + 2.

Use the known facts of 9 × 5 and 9 × 2.

The array shows that 9 × ____ plus 9 × ____ equals

____ × 7

The unknown is ____.

So, 9 × 7 = ____. There are ___ beetels on display.

Answer:

Given that,

A museum has a display of 9 kinds of beetles.

There are 7 of each kind of beetle.

Here 9 x 7 = 63.

Decompose the factor 7 into addends of 5 + 2.

The known facts of 9 × 5 and 9 × 2.

9 x 5 = 45.

9 x 2 = 18.

45 + 18 = 63.

The array shows that 9 × 5 plus 9 × 2 equals

9 × 7

The unknown is 63.

So, 9 × 7 = 63.

There are 63 beetles on display.

To multiply by 7, you can also use a related fact.

Example 2

A pet store sold 3 gerbils. Each gerbil cost $7. How much money did the pet store make selling the gerbils?

Write 3 groups of $7 as 3 × $7 or you can write it vertically.

Use the Commutative Property of Multiplication.

You know 7 × 3 = ____. Turn the array. 3 × 7 = ____

So, 3 × 7 = ____

The pet store made $____ on the sale of the gerbils.

Answer:

Given that,

A pet store sold 3 gerbils.

Each gerbil cost $7.

3 groups of $7 is 3 × $7

Know 7 × 3 = 21.

Turn the array. 3 × 7 = 21.

The pet store made $21on the sale of the gerbils.

**Guided Practice**

**Use a known fact and the Commutative Property to find each product.**

Question 1.

7 × 5 = ____

known fact: 5 × 7 = ____

Answer:

Multiplication of 7 with 5 then you get 35.

7 x 5 = 35

The known fact is 5 x 7 = 35

It is a commutative property of multiplication.

Question 2.

7 × 2 = ____

known fact: 2 × ___ = ____

Answer:

Multiplication of 7 with 2 then you get 14.

7 x 2 = 14.

The known fact is 2 x 7 = 14.

It is a commutative property of multiplication.

**Talk Math**

Describe two different strategies A for multiplying a number by 7.

Answer:

The one strategies is using the multiplication table

7 x 5 = 35.

The second strategies is doubling the known facts.

Decompose 7 with 5 + 2.

5 x 5 = 25.

5 x 2 = 10.

Add 25 + 10 = 35.

In both methods the product is 35.

**Independent Practice**

**Algebra Find each unknown. Decompose the factor 7 into 5 + 2.**

Question 3.

7 × 7 =

known fact: 7 × 5 = ____

7 × 2 = ____

The unknown is ____.

Answer:

Multiplication of 7 with 7 then you get 49.

7 x 7 = 49.

Decompose 7 with 5 + 2.

The known fact is 7 x 5 = 35.

7 x 2 = 14.

Known add the two products 35 + 14 = 49.

The unknown is 49.

Question 4.

8 × 7 =

known fact: 8 × 5 = ____

8 × 2 = ____

The unknown is ____.

Answer:

Multiplication of 8 with 7 then you get 56.

8 x 7 = 56.

Decompose 7 into 5 + 2.

The known fact is 7 x 5 = 35.

7 x 2 = 14.

Known add the two products 35 + 14 = 56.

The unknown is 56.

**Use a known fact and the Commutative Property to find each product.**

Question 5.

7 × 1 = ____

known fact:

_______

Answer:

Multiplication of 7 with 1 then you get 7.

7 x 1= 7.

The known fact is 1 x 7 = 7.

It is a commutative property of multiplication.

Question 6.

7 × 2 = ____

known fact:

_______

Answer:

Multiplication of 7 with 2 then you get 14.

7 x 2 = 14.

The known fact is 2 x 7 = 14.

It is the commutative property of multiplication.

Question 7.

7 × 10 = ____

known fact:

_______

Answer:

Multiplication of 7 with 10 then you get 70.

7 x 10 = 70.

The known fact is 10 x 7 = 70.

It is the commutative property of multiplication.

Question 8.

7 × 0 = ____

known fact:

_______

Answer:

Multiplication of 7 with 0 then you get 0.

7 x 0 = 0.

The known fact is 0 x 7 = 0.

It is the commutative property of multiplication.

Question 9.

7 × 3 = ____

known fact:

_______

Answer:

Multiplication of 7 with 3 then you get 21.

7 x 3 = 21.

The known fact is 3 x 7 = 21.

It is the commutative property of multiplication.

Question 10.

7 × 6 = ____

known fact:

_______

Answer:

Multiplication of 7 with 6 then you get 42.

7 x 6 = 42.

The known fact is 6 x 7 = 42.

It is the commutative property of multiplication.

**Algebra Find each unknown. Use the Commutative Property.**

Question 11.

5 × = 35

× 5 = 35

The unknown is ____.

Answer:

Multiplication of 5 with 7 then you get 35.

5 x 7 = 35.

7 x 5 = 35.

It is the commutative property of multiplication.

The unknown is 7.

Question 12.

3 × 7 =

7 × 3 =

The unknown is ____.

Answer:

Multiplication of 3 with 7 then you get 21.

3 x 7 = 21.

7 x 3 = 21.

It is the commutative property of multiplication.

The unknown is 21.

Question 13.

7 × = 70

× 7 = 70

The unknown is ____.

Answer:

Multiplication of 7 with 10 then you get 70.

7 x 10 = 70.

10 x 7 = 70.

It is the commutative property of multiplication.

The unknown is 70.

**Multiply.**

Question 14.

Answer:

Multiplication of 7 with 3 then you get 21.

7 x 3 = 21.

Question 15.

Answer:

Multiplication of 7 with 1 then you get 7.

7 x 1 = 7.

Question 16.

Answer:

Multiplication of 7 with 4 then you get 28.

7 x 4 = 28.

Question 17.

Answer:

Multiplication of 7 with 8 then you get 56.

7 x 8 = 56.

**Problem Solving**

**Algebra For Exercises T 8 and 19, write a multiplication sentence with a symbol for the unknown. Solve.**

Question 18.

Ryan and his 5 friends scored 7 points each while playing basketball. What is their total points?

Answer:

Given that,

Ryan and his 5 friends scored 7 points each while playing basketball.

The total number of persons are 5 + 1 = 6.

Each person has 7 points.

So, 6 x 7 = 42.

Therefore the total number of points are 42.

Question 19.

Inez has 8 CDs. How many songs are there if each CD has 7 songs?

Answer:

Given that,

Inez has 8 CDs.

The total number of songs in each CD is 7.

The total number of songs in 8 CDs is 8 x 7 = 56.

Therefore the total number of songs are 56.

**HOT Problems**

Question 20.

**Mathematical PRACTICE 8 Look for a Pattern** Look at the multiplication table. Color the row and column of products of 7. Describe a pattern.

Answer:

The products of 7 are

7 x 1 = 7.

7 x 2 = 14.

7 x 3 = 21.

7 x 4 = 28.

7 x 5 = 35.

7 x 6 = 42.

7 x 7 = 49.

7 x 8 = 54.

7 x 9 = 63.

7 x 10 = 70.

Question 21.

**Mathematical PRACTICE 3 Find the Error** Circle the multiplication sentence which is incorrect. Explain.

7 × 7 = 48 7 × 9 = 63 5 × 7 = 35

Answer:

The circle one is not an array.

Because 7 x 7 = 49.

Question 22.

**? Building on the Essential Question** Compare finding products using the Commutative Property of Multiplication and using related multiplication facts.

Answer:

The products using the Commutative Property of Multiplication is

3 x 4 = 12.

4 x 3 = 12.

The commutative property says that the order in which we multiply numbers does not change the products.

### McGraw Hill My Math Grade 3 Chapter 8 Lesson 2 My Homework Answer Key

**Practice**

**Algebra Find each unknown. Decompose the factor 7 into 5 + 2.**

Question 1.

7 × 10 =

Known facts: 5 × 10 = ___

2 × 10 = ____

The unknown is ____

Answer:

Multiplication of 7 with 10 then you get 70.

7 x 10 = 70.

Decompose 7 with 5 + 3.

Known fact is 5 x 10 = 50.

2 x 10 = 20.

Add 50 + 20 = 70.

The unknown is 70.

Question 2.

5 × 7 =

Known facts: 5 × 5 = ___

5 × 2 = ____

The unknown is ____

Answer:

The multiplication of 5 with 7 then you get 35.

The known fact is 5 x 5 = 25.

5 x 2 = 10.

Add 25 + 10 = 35.

The unknown is 35

**Algebra Find each unknown. Use the Commutative Property.**

Question 3.

7 × 3 =

3 × 7 =

The unknown is ____

Answer:

Multiplication of 7 with 3 then you get 21.

7 x 3 = 21.

3 x 7 = 21.

It is a commutative property of multiplication.

The unknown is 21.

Question 4.

7 × = 28

× 7 = 28

The unknown is ____

Answer:

Multiplication of 7 with 4 then you get 28.

7 x 4 = 28.

4 x 7 = 28.

It is a commutative property of multiplication.

The unknown is 4.

Question 5.

× 7 = 49

7 × = 49

The unknown is ____

Answer:

Multiplication of 7 with 7 then you get 49.

7 x 7 = 49.

7 x 7 = 49.

It is a commutative property of multiplication.

The unknown is 7.

Question 6.

7 × = 14

× 7 = 14

The unknown is ____

Answer:

Multiplication of 7 with 2 then you get 14.

7 x 2 = 14.

2 x 7 = 14.

It is a commutative property of multiplication.

The unknown is 2.

**Problem Solving**

**Algebra Write a multiplication sentence with a symbol for the unknown. Then solve.**

Question 7.

**Mathematical PRACTICE 4 Model Math** It takes Callie 9 minutes to paint each slat on a fence. There are 7 slats in each section of the fence. How long will it take Callie to paint each section of the fence?

Answer:

Given that,

The Callie take to paint each slat on a fence is 9 minutes.

The total number of slats is 7.

So, 9 x 7 = 63.

Therefore the time taken to Callie to paint each section of the fence is 63 minutes.

Question 8.

Each house on Mulberry Street has 7 front windows. There are 3 houses on each side of the street. How many front windows are there in all?

Answer:

Given that,

Each house on Mulberry Street has 7 front windows.

There are 3 houses on each side of the street.

So, 7 x 3 = 21.

Therefore the total number of front windows in all are 21.

**Test Practice**

Question 9.

A bicycle shop is replacing both tires on 7 bikes. How many tires will be replaced altogether?

A. 2 tires

B. 7 tires

C. 9 tires

D. 14 tires

Answer:

Given that,

A bicycle shop is replacing both tires on 7 bikes.

The bike has 2 tires.

So, 2 x 7 = 14.

Therefore the total number of tires are 14.

Option D is the correct answer.