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.