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.