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

All the solutions provided inÂ 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 Ă— 6.
Decompose, or separate, the number 4 into equal addends of 2 + 2.

1. Model the known fact, 2 Ă— 6.
Use counters to make an array. Show 2 rows of 6. Draw your array.
Write the number sentence.
_____________ Ă— ______________ = ______________

2. Double the known fact.
Make one more 2 Ă— 6 array. Draw your array.
Write the number sentence for this array.
_____________ Ă— _____________ = ______________
12 + ___________ = ___________

3. Find 4 Ă— 6.
Push the two arrays together. Write the new number sentence.
____________ Ă— _____________ = ______________
2 Ă— 6 plus 2 Ă— 6 = ______________
So, 4 Ă— 6 = ____________
The number sentence is 2 x 6 = 12.
The array of 2 x 6 = 12.

One more array is 2 Ă— 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 Ă— 5.
Decompose 6 into two equal addends. 6 = 3 + ______________
1. Model the known fact, 3 Ă— 5 two times.
Draw two 3 Ă— 5 arrays.
Write the product on each array.

2. Double the known fact 3 Ă— 5.
Draw the two arrays pushed together. Add the products.
15 + ____________ = ______________

3. Find 6 Ă— 5.
Write the multiplication sentence.
___________ Ă— __________ = ____________
3 Ă— 5 plus 3 Ă— 5 = ___________.
So, 6 Ă— 5 = ______________.
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.

Question 1.
Why can you double the product of 2 Ă— 6 to find 4 Ă— 6?
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.
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.
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 Ă— 5. Label the arrays with a number sentence.
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 Ă— 3 = ______________
Known fact: 2 Ă—3 = _______________
Double the product: 6 + 6 = _______________

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 Ă— 4 = _______________
Known fact: 2 Ă— 4 = _______________
Double the product: 8 + 8 = _______________
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 Ă— 4 = _______________
Known fact: _______________
Double the product: _______________
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 Ă— 7 = _______________
Known fact: _______________
Double the product: _______________
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 Ă— 8 = _____________
3 Ă— 8 = ______________
___________ Ă— ____________ = ___________
Multiplication of 3 with 8 then you get 24
3 x 8 = 24.
3 x 8 = 24.
24 + 24 = 48.
Know add 3 x 8 + 3 x 8 = 6 x 8.
Therefore 6 x 8 = 48.

Question 10.
3 Ă— 6 = ______________
3 Ă— 6 = ______________
___________ Ă— ____________ = ___________
Multiplication of 3 with 6 then you get 18.
3 x 6 = 18.
3 x 6 = 18.
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? ____________
Given that,
Each tray has 2 rows of 6 cookies.
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 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? ____________
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 Ă— 6? Explain.
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.

Question 14.
When is doubling a known fact useful?
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 Ă— 5. Draw the model two times.
4 Ă— 5 = _____________
Known fact: 2 Ă— 5 = _____________
Double the product: 10 + 10 = _____________
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 Ă— 7 = _____________
3 Ă— 7 = _____________
____________ Ă— _____________ = _____________
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 6Â  x 7 = 42.

Question 3.
3 Ă— 3 = _____________
3 Ă— 3 = _____________
____________ Ă— ____________ = ______________
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 Ă— 6 = _____________
2 Ă— 6 = _____________
____________ Ă— ____________ = ______________
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 Ă— 9 = _____________
2 Ă— 9 = _____________
____________ Ă— ____________ = ______________
Multiplication of 2 with 9 then you get 18.
2 x 9 = 18.
2 x 9 = 18.
18 is 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?
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?
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?
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.