All the solutions provided in **McGraw Hill Math Grade 3 Answer Key PDF Chapter 8 Lesson 5 Multiply by 9** will give you a clear idea of the concepts.

## McGraw-Hill My Math Grade 3 Answer Key Chapter 8 Lesson 5 Multiply by 9

**Math in My World**

Example 1

Butterflies gathered on 5 branches of a tree. There are 9 butterflies on each branch. What is the total number of butterflies on the tree?

Find 5 × 9 = .

One Way Use the Commutative Property.

Think 9 × 5 = ____ ← Use a known fact and Commutative Property

Use a known fact and Commutative Property.

The unknown is ___. There are ____ butterflies on the tree.

Another Way Subtract from a known 10s fact.

You know 5 × 10 = ___.

So, 5 × 9 = ___. The unknown is ___.

There are ___ butterflies on the tree.

Answer:

Given that,

Butterflies gathered on 5 branches of a tree.

There are 9 butterflies on each branch.

So, 9 x 5 = 45.

The unknown is 45.

There are 45 butterflies on the tree.

The another way is subtraction

10 x 5 = 50

In 1 row there are 5 butterflies.

Subtract 5 from 50 then you get 45.

So, 5 × 9 = 45.

The unknown is 45.

There are 45 butterflies on the tree.

Example 2

Refer to the multiplication table.

Describe the pattern among the 9s facts Then use the pattern to find 8×9.

1. Shade the row green that gives the products with a factor of 9.

2. Beginning with 18, the tens digit in each product is 1 less than the factor that is not 9. The sum of the digits in each product is 9.

So, 8 × 9 = ____

Answer:

The factors of 9 are shaded with green.

So, 8 x 9 = 72.

**Talk Math**

How can patterns help you when multiplying by 9?

Answer:

All multiplies of 9 are less than 10.

Subtract 10 – 1 then you get 9. It is the multiple of 9.

The 9 is odd.

9 x 2 = 18.

9 + 9 = 18.

18 is the even.

Multiplies of 9 are even or odd.

**Guided Practice**

**Use the Commutative Property to find each product or missing factor.**

Question 1.

2 × 9 = ____

___ × ___ = ____

Answer:

Commutative property states that if change in order of the numbers in multiplication the product does not change.

Multiplication of 2 with 9 then you get 18.

2 x 9 = 18.

9 x 2 = 18.

The missing factors are 9, 2.

The missing product is 18.

Question 2.

4 × 9 = ____

___ × ___ = ____

Answer:

Commutative property states that if change in order of the numbers in multiplication the product does not change.

Multiplication of 4 with 9 then you get 36.

4 x 9 = 36.

9 x 4 = 36.

The missing factors are 4, 9.

The missing product is 36.

Question 3.

Answer:

Multiplication of 3 with 9 then you get 27.

3 x 9 = 27.

It is the commutative property.

Question 4.

Answer:

Multiplication of 5 with 9 then you get 45.

5 x 9 = 45.

It is a commutative property.

**Independent Practice**

**Use the Commutative Property to find each product. Write a related multiplication fact.**

Question 5.

6 × 9 = ____

___ × ___ = ____

Answer:

Using the commutative property

Multiplication of 6 with 9 then you get 54.

6 x 9 = 54.

The related multiplication fact is

9 x 4 = 54.

Question 6.

20 × 9 = ____

Answer:

Using the commutative property

Multiplication of 20 with 9 then you get 180.

20 x 9 = 180.

The related multiplication fact is

9 x 20 = 180.

Question 7.

7 × 9 = ___

Answer:

Using the commutative property

Multiplication of 7 with 9 then you get 63.

7 x 9 = 63.

The related multiplication fact is

9 x 7 = 63.

Question 8.

Answer:

Using the commutative property

Multiplication of 8 with 9 then you get 72.

8 x 9 = 72.

Question 9.

Answer:

Using the commutative property

Multiplication of 1 with 9 then you get 9.

1 x 9 = 9.

Question 10.

Answer:

Using the commutative property

Multiplication of 3 with 9 then you get 27.

3 x 9 = 27.

**Draw an array for a known 10s fact. Then subtract 1 from each row to find each product.**

Question 11.

4 × 9 = ____

Known fact: ____ × ___ = _____

40 – ___ = ____

Answer:

Multiplication of 4 with 9 then you get 36.

4 x 9 = 36.

We know that the 10’s fact is 4 x 10 = 40.

The array of 4 x 10 is

Know subtract 1 from each row.

Subtract 40 – 4 = 36.

The product is 36.

Question 12.

5 × 9 = ____

Known fact: ____ × ___ = _____

50 – ___ = ____

Answer:

Multiplication of 5 with 9 then you get 45.

5 x 9 = 45.

We know that the 10’s fact is 5 x 10 = 50.

The array of 5 x 10 is

Know subtract 1 from each row.

50 – 5 = 45.

45 is the product.

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

Question 13.

9 × 10 = .

? × 9 = 90

= ____

? = ____

Answer:

Multiplication of 9 with 10 then you get 90.

9 x 10 = 90.

10 x 9 = 90.

It is commutative property.

The unknown is 90.

? = 10.

Question 14.

9 × 2 = .

? × 9 = 18

= ____

? = ____

Answer:

Multiplication of 9 with 2 then you get 18.

9 x 2 = 18.

2 x 9 = 18.

It is a commutative property.

The unknown is 18.

? = 18.

Question 15.

9 × 8 = .

? × 9 = 72

= ____

? = ____

Answer:

Multiplication of 9 with 8 then you get 72.

9 x 8 = 72.

8 x 9 = 72.

It is commutative property.

The unknown is 72.

? = 9.

**Problem Solving**

**Mathematical PRACTICE 4 Model Math Write a multiplication sentence with a symbol for the unknown. Then solve.**

Question 16.

Lyle caught 3 buckets of crayfish. He put 9 crayfish in each bucket. How many crayfish did Lyle catch?

Answer:

Given that,

Lyle caught 3 buckets of crayfish.

There are 9 crayfish in each bucket.

The total number of crayfish did Lyle catch is 9 x 3 = 27.

Therefore the total number of crayfish cached by Lyle is 27.

Question 17.

Cecilia needs to make 8 color copies of her babysitting flyer. The copy machine charges 9⊄ a copy. How much will the 8 copies cost Cecilia?

Answer:

Given that,

Cecilia needs to make 8 color copies of her babysitting flyer.

The copy machine charges 9 cents for each copy.

The cost for 8 copies are 8 x 9 cents = 72 cents.

Question 18.

There were 4 car races on Saturday and 3 on Sunday. If there were 9 cars racing in each race, how many cars raced over the two days?

Answer:

Given that,

The total number of car races on Saturday is 4.

The total number of car races on Sunday is 3.

The total number of cars in each race is 9.

The total number of races are 4 + 3 = 7.

The number of cars in the 2 races are 7 x 9 = 63.

Therefore number of cars in raced over the two days is 63.

**HOT Problems**

Question 19.

**Mathematical PRACTICE 3 Find the Error** Eva says she can find the product of 9 × 9 by finding 9 × 8 = 72, then adding 8 more. So, she says 9 × 9 = 80. Find and correct her mistake.

Answer:

Given that,

Eva done the mistake to find the 9 x 9.

The correct answer is

We know that 9 x 8 = 72.

For finding 9 x 9 add 9 to the 72.

Then 72 + 9 = 81.

9 x 9 = 81.

Question 20.

**? Building on the Essential Question** How can the 10s facts help me solve the 9s facts? Explain.

Answer:

For the 9’s facts we can also use the 10’s facts by subtracting 1 group from the 10’s facts.

For example 9 x 3 = 27.

10 x 3 = 30.

Subtract 1 group means 3.

30 – 3 = 27.

So, 9 x 3 = 27.

### McGraw Hill My Math Grade 3 Chapter 8 Lesson 5 My Homework Answer Key

**Practice**

**Use the Commutative Property to find each product or missing factor.**

Question 1.

Answer:

Commutative property states that if change in order of the numbers in multiplication the product does not change.

Question 2.

Answer:

Commutative property states that if change in order of the numbers in multiplication the product does not change.

Question 3.

Answer:

Commutative property states that if change in order of the numbers in multiplication the product does not change.

**Draw an array for a known 10s fact. Then subtract 1 from each row to find the product.**

Question 4.

6 × 9 = ____

Known fact: ___ × ___ = ____

60 – ____ = _____

Answer:

Multiplication of 6 with 9 then you get 54.

The know fact is 6 x 10 = 60.

The array of 6 x 10 is

Subtract 1 from each row.

Then 60 – 6 = 54.

The product is 54.

Question 5.

4 × 9 = ____

Known fact: ___ × ___ = ____

____ – ____ = _____

Answer:

Multiplication of 4 with 9 then you get 36.

The known fact is 4 x 10 = 40.

The array of 4 x 10 is

Subtract 1 from each row.

Then 40 – 4 = 36.

The product is 36

**Algebra Use the Commutative Property to find each unknown.**

Question 6.

9 × = 36

× 9 = 36

The unknown is ____.

Answer:

Multiplication of 9 with 4 then you get 36.

9 x 4 = 36.

4 x 9 = 36.

The unknown is 36.

Question 7.

× 9 = 72

9 × = 72

The unknown is ____.

Answer:

Multiplication of 7 with 9 then you get 63.

7 x 9 = 63.

9 x 7 = 63.

The unknown is 7.

**Problem Solving**

Question 8.

**Mathematical PRACTICE 3 Justify Conclusions** Ty works 9 hours a day and earns $6 an hour. Cal works 6 hours a day and earns $9 an hour. If they both work 5 days, who earns more money? Who works longer? Explain.

Answer:

Given that,

Ty works 9 hours a day and earns $6 an hour.

The number of hours Ty work for 5 days is 5 x 9 = 45 hours.

Cal works 6 hours a day and earns $9 an hour.

The number of hours Cal work for 5 days is 5 x 6 = 30 hours.

Ty earn for 5 days is 45 x 9 = $405.

Cal earn for 5 days is 30 x 5 = $150.

Therefore Ty earned more than Cal and Ty works longer.

**Test Practice**

Question 9.

Anna lives 9 blocks from school. How many blocks does she walk to school in 3 days?

A. 6 blocks

B. 9 blocks

C. 12 blocks

D. 27 blocks

Answer:

Given that,

The Anna lives 9 blocks from school.

The total number of days are 3.

So, 9 x 3 = 27

Therefore the 27 blocks that Anna walk to school in 3 days.

Option D is the correct answer.