All the solutions provided in **McGraw Hill My Math Grade 3 Answer Key PDF Chapter 7 Lesson 3 Double a Known Fact **will give you a clear idea of the concepts.

## McGraw-Hill My Math Grade 3 Answer Key Chapter 7 Lesson 3 Double a Known Fact

A known fact is a fact you have memorized. You can use a known multiplication fact to solve a multiplication fact you do not know.

**Build It**

Find 4 × 6.

Decompose, or separate, the number 4 into equal addends of 2 + 2.

1. Model the known fact, 2 × 6.

Use counters to make an array. Show 2 rows of 6. Draw your array.

Write the number sentence.

_____________ × ______________ = ______________

2. Double the known fact.

Make one more 2 × 6 array. Draw your array.

Write the number sentence for this array.

_____________ × _____________ = ______________

Add the two products together.

12 + ___________ = ___________

3. Find 4 × 6.

Push the two arrays together. Write the new number sentence.

____________ × _____________ = ______________

2 × 6 plus 2 × 6 = ______________

So, 4 × 6 = ____________

Answer:

The number sentence is 2 x 6 = 12.

The array of 2 x 6 = 12.

One more array is 2 × 6.

Know add the two arrays that is 2 x 6 + 2 x 6 = 4 x 6.

4 x 6 = 12.

**Try It**

Find 6 × 5.

Decompose 6 into two equal addends. 6 = 3 + ______________

1. Model the known fact, 3 × 5 two times.

Draw two 3 × 5 arrays.

Write the product on each array.

2. Double the known fact 3 × 5.

Draw the two arrays pushed together. Add the products.

15 + ____________ = ______________

3. Find 6 × 5.

Write the multiplication sentence.

___________ × __________ = ____________

3 × 5 plus 3 × 5 = ___________.

So, 6 × 5 = ______________.

Answer:

The multiplication of 6 with 5 then you get 30.

Decompose 6 into 3 + 3.

Know draw the two arrays

3 x 5 and 3 x 5.

And

The multiplication sentence is 3 x 5 = 15.

Add 3 x 5 + 3 x 5

So, 6 x 5 = 30.

**Talk About It**

Question 1.

Why can you double the product of 2 × 6 to find 4 × 6?

Answer:

2 x 6 = 12.

Multiplication of 2 with 6 then you get 12.

The product is 12.

Double the product is 12 + 12 = 24.

multiplication of 4 with 6 then you get 24.

4 x 6 = 24.

Therefore double the product of 2 x 6 is the product of 4 x 6.

Question 2.

What doubles fact would 3 × 6 help you find?

Answer:

Multiplication of 3 with 6 then you get 18.

3 x 6 = 18.

If we double the 3 x 3 it is.

3 x 3 = 9.

Double the product is 9 + 9 = 18.

Question 3.

Give an example of doubling a known fact. Explain.

Answer:

The multiplication of 2 x 3 = 6.

6 is the product.

Double the product is 6 + 6 = 12.

2 x 3 + 2 x 3 = 4 x 3.

4 x 3 = 12.

Question 4.

Draw two arrays that you could put together to find 4 × 5. Label the arrays with a number sentence.

Answer:

Multiplication of 4 with 5 then you get 20.

The two number sentences is

4 x 5 = 20.

The array of 4 x 5 is

The array of 4 x 5 is

Add 4 x 5 + 4 x 5 = 8 x 5.

8 x 5 = 40.

**Practice It**

**Use counters to model a known fact that will help you find the first product. Draw the model two times.**

Question 5.

4 × 3 = ______________

Known fact: 2 ×3 = _______________

Double the product: 6 + 6 = _______________

Answer:

Multiplication of 4 with 3 then you get 12.

4 x 3 = 12

Known fact is 2 x 3 = 6.

Double the product is 6 + 6 = 12.

The array of 4 x 3

The another array of 2 x 3

Question 6.

4 × 4 = _______________

Known fact: 2 × 4 = _______________

Double the product: 8 + 8 = _______________

Answer:

Multiplication of 4 with 4 then you get 16.

4 x 4 = 16.

The known fact is 2 x 4 = 8.

The product is 8.

Double the product is 8 + 8 = 16.

The array of 4 x 4

The another array of 2 x 4

Question 7.

7 × 4 = _______________

Known fact: _______________

Double the product: _______________

Answer:

Multiplication of 7 with 4 then you get 28.

7 x 4 = 28.

The known fact is 7 x 2 = 14.

The product is 14.

Double the product is 14 + 14 = 28.

The array of 7 x 4

The another array of 7 x 2

Question 8.

6 × 7 = _______________

Known fact: _______________

Double the product: _______________

Answer:

Multiplication of 6 with 7 then you get 42.

6 x 7 = 42.

The known fact is 3 x 7 = 21.

The product is 21.

Double the product is 21+ 21 = 42.

The array of 6 x 7

The another array of 3 x 7

**Use counters to double the known fact. Write the product it helps you find.**

Question 9.

3 × 8 = _____________

3 × 8 = ______________

___________ × ____________ = ___________

Answer:

Multiplication of 3 with 8 then you get 24

3 x 8 = 24.

3 x 8 = 24.

Know add the two products

24 + 24 = 48.

Know add 3 x 8 + 3 x 8 = 6 x 8.

Therefore 6 x 8 = 48.

Question 10.

3 × 6 = ______________

3 × 6 = ______________

___________ × ____________ = ___________

Answer:

Multiplication of 3 with 6 then you get 18.

3 x 6 = 18.

3 x 6 = 18.

Known add the two products.

18 + 18 = 36.

Add 3 x 6 + 3 x 6 = 6 x 6.

Therefore 6 x 6 = 36.

**Apply It**

Question 11.

Megan and Paul each have a tray of cookies. Each tray has 2 rows of 6 cookies. How many cookies do they have if they put their trays together?

What known fact did you double? ____________

What fact is found by doubling the known fact? ____________

Answer:

Given that,

Each tray has 2 rows of 6 cookies.

2 x 6 = 12.

2 x 6 = 12.

The product is 12.

Known add the two products

12 + 12 = 24.

Add 2 x 6 + 2 x 6 = 4 x 6.

Therefore 4 x 6 = 24.

Question 12.

**Mathematical PRACTICE** Model Math Two heart buttons have 8 holes. Jeffery doubles the number of heart buttons shown. How many holes will there be now?

What known fact did you double? ____________

What fact is found by doubling the known fact? ____________

Answer:

Given that,

Two heart buttons have 8 holes.

Double the holes is 8 + 8 = 16.

Therefore there are 16 holes at now.

Question 13.

**Mathematical PRACTICE** Justify Conclusions Can you double a known fact to find 7 × 6? Explain.

Answer:

Multiplication of 7 with 6 equal to 42.

42 is the product.

Double the product is 42 + 42 = 84.

Add 7 + 7 = 14.

14 x 6 = 84.

14 x 6 is the double of 7 x 6.

**Write About It**

Question 14.

When is doubling a known fact useful?

Answer:

Doubling a fact is useful to add the number by itself then it get.

The double fact of 14 is.

7 + 7 = 14.

### McGraw Hill My Math Grade 3 Chapter 7 Lesson 3 My Homework Answer Key

**Practice**

Question 1.

Draw counters to model a known fact that will help you find 4 × 5. Draw the model two times.

4 × 5 = _____________

Known fact: 2 × 5 = _____________

Double the product: 10 + 10 = _____________

Answer:

Multiplication of 4 with 5 then you get 20.

4 x 5 = 20.

The known fact is 2 x 5 = 10.

Double the product 10 + 10 = 20.

The array of 4 x 5.

The array of 2 x 5.

**Double the known fact. Write the product it helps you find.**

Question 2.

3 × 7 = _____________

3 × 7 = _____________

____________ × _____________ = _____________

Answer:

Multiplication of 3 with 7 then you get 21.

3 x 7 = 21.

3 x 7 = 21.

21 is the product.

21 + 21 = 42.

Know add 3 x 7 + 3 x 7 = 6 x 7.

Therefore 6 x 7 = 42.

Question 3.

3 × 3 = _____________

3 × 3 = _____________

____________ × ____________ = ______________

Answer:

Multiplication of 3 with 3 then you get 9.

3 x 3 = 9.

3 x 3 = 9.

The product is 18.

18 + 18 = 36.

Add 3 x 3 + 3 x 3 = 6 x 3.

Question 4.

2 × 6 = _____________

2 × 6 = _____________

____________ × ____________ = ______________

Answer:

Multiplication of 2 with 6 then you get 12.

2 x 6 = 12.

2 x 6 = 12.

The product is 12.

12 + 12 = 24.

Add 2 x 6 + 2 x 6 = 4 x 6.

Therefore 4 x 6 = 24.

Question 5.

2 × 9 = _____________

2 × 9 = _____________

____________ × ____________ = ______________

Answer:

Multiplication of 2 with 9 then you get 18.

2 x 9 = 18.

2 x 9 = 18.

18 is the product.

Know add the product

18 + 18 = 36.

Add 2 x 9 + 2 x 9 = 4 x 9.

Therefore 4 x 9 = 36.

**Problem Solving**

**Double a known fact to solve.**

Question 6.

Dr. Berry sees 3 patients every hour. If she works 8 hours, how many patients does she see?

Answer:

Given that,

Dr. Berry sees 3 patients every hour.

If she works 8 hours.

The patient does she see is 3 x 8 = 24.

Therefore Dr. Berry sees 24 hours for 8 hours.

Question 7.

The Johnson twins and the Clayton twins went to the fair. Each child rode 5 rides. What is the total number of times all four children went on a ride?

Answer:

Given that,

Each child rode 5 rides.

The total number of times all four children went on a ride is 5 x 4 = 20.

Therefore all the four children went on ride for 20 times.

Question 8.

**Mathematical PRACTICE** Identify Structure Vince drinks 4 large glasses of water each day. How many glasses of water does Vince drink in 7 days?

Answer:

Given that,

Vince drinks 4 large glasses of water each day.

If he drinks the water for 7 days is 7 x 4 = 28.

Therefore Vince drinks 28 large glasses of water in 7 days.

**Vocabulary Check**

**Choose the correct word(s) to complete each sentence.**

known fact

decompose

Question 9.

One way to _______________ the number 8 is to write it as 4 + 4.

Answer:

One way to decompose the number 8 is to write it as 4 + 4.

Question 10.

A fact that you have memorized is a _______________.

Answer:

A fact that you have memorized is a known fact.