All the solutions provided in McGraw Hill My Math Grade 3 Answer Key PDF Chapter 7 Lesson 1 Multiply by 3 will give you a clear idea of the concepts.
McGraw-Hill My Math Grade 3 Answer Key Chapter 7 Lesson 1 Multiply by 3
Math in My World
Example 1
There are 3 dogs. Each dog buried 4 bones in a yard. How many bones are buried in the yard?
Find 3 × 4.
Write it like this, also.
One Way: Use an array.
Find 3 rows of 4 bones.
The array shows that 3 × 4 = ______________.
There are ______________ bones buried in the yard.
Use the Commutative Property to write another multiplication sentence for this array.
______________ × ______________ = ______________
Another Way: Use a number line.
Skip count to find 3 groups of 4.
The number line shows ______________ jumps of 4 is ______________.
So, 3 × 4 = ______________. There are ______________ bones buried in the yard.
Answer:
Given that,
There are 3 dogs.
Each dog buried 4 bones in a yard.
One way is
The number of bones that the dog buried is
The array shows that 3 × 4 = 12
There are 12 bones buried in the yard.
Use the Commutative Property to write another multiplication sentence for this array is 3 x 4 = 12.
The another way is
Skip count to find 3 groups of 4.
The number line shows 3 jumps of 4 is 12.
So, 3 × 4 = 12. There are 12 bones buried in the yard.
Example 2
Luke bought 15 packs of seeds. How many different kinds of seeds does he have if there are 3 of each kind? Find the unknown factor. Use a related multiplication fact.
You know that 3 × 5 = 15.
So, the ______________ Property tells you that ______________ × 3 = 15, also.
The unknown factor is ______________.
Check:
Answer:
Given that,
Luke bought 15 packs of seeds.
The different kinds of seeds does he have if there are 3 of each kind is
You know that 3 × 5 = 15.
So, the multiplication Property tells you that 5 × 3 = 15, also.
The unknown factor is 5.
Talk Math
Explain two strategies you can use to find the product of 7 × 3.
Answer:
The two strategies to find the product of 7 × 3 is
7 x 3 = 21.
3 x 7 = 21.
Guided Practice
Question 1.
Draw an array. Then write two multiplication sentences.
3 rows of 2
Answer:
The array of 3 rows of 2 is
The two multiplication sentence is
3 x 2 = 6.
2 x 3 = 6.
Question 2.
Circle the number sentence that is represented by the number line.
15 × 1 = 15
3 × 5 = 15
5 + 10 = 15
Answer:
The number sentence that is represented by the number line is 3 x 5 = 15.
Independent Practice
Draw an array for each. Then write two multiplication sentences.
Question 3.
3 rows of 4
Answer:
The array of 3 rows of 4 is
The two multiplication sentence is
3 x 4 = 12
4 x 2 = 12.
Question 4.
7 rows of 3
Answer:
The array of 7 rows of 3 is
The two multiplication sentence is
7 x 3 = 21.
3 x 7 = 21.
Question 5.
3 rows of 8
Answer:
The array of 3 rows of 8 is
The two multiplication sentence is
3 x 8 = 24.
8 x 3 = 24.
Question 6.
5 rows of 3
Answer:
The array of 5 rows of 3 is
The two multiplication sentence is
5 x 3 = 15.
3 x 5 = 15.
Draw jumps on the number line to find each product.
Question 7.
3 × 6 = _____________
Answer:
3 x 6 = 18.
The multiplication of 3 with 6 then you get 18.
To draw the jumps on the number line we need to subtract multiple times that is
18 – 3 = 15.
15 – 3 = 12.
12 – 3 = 9.
9 – 3 = 6.
6 – 3 = 3.
3 – 3 = 0.
Question 8.
3 × 9 = _____________
Answer:
3 x 9 = 27.
Multiplication of 3 with 9 then you get 27.
To draw the jumps on the number line we need to subtract multiple times that is
27 – 3 = 24.
24 – 3 = 21.
21 – 3 = 18.
18 – 3 = 15.
15 – 3 = 12.
12 – 3 = 9.
9 – 3 = 6.
6 – 3 = 3.
3 – 3 = 0.
Algebra Find the unknown fador. Use the Commutative Property.
Question 9.
× 3 = 24
3 × = 24
The unknown is _____________.
Answer:
we know that,
8 x 3 = 24.
3 x 8 = 24.
It is a commutative property of multiplication.
The unknown factor is 8.
Question 10.
3 × = 15
× 3 = 15
The unknown is _______________.
Answer:
We know that,
3 x 5 = 15.
5 x 3 = 15.
It is commutative property of multiplication.
The unknown factor is 5.
Question 11.
3 × = 6
× 3 = 6
The unknown is _______________.
Answer:
We know that,
3 x 2 = 6.
2 x 3 = 6.
It is commutative property of multiplication.
The unknown factor is 2.
Problem Solving
Question 12.
There are 9 singers. They each perform 3 songs at the recital. How many songs were performed?
Answer:
Given that,
The total number of singers is 9.
They each perform 3 songs at the recital.
The number of songs performed is 9 x 3 = 27.
Therefore they performed the 27 songs.
Question 13.
There are 7 daisies and 7 tulips. Each flower has 3 petals. How many petals are there in all?
Answer:
Given that,
There are 7 daisies and 7 tulips.
The total number of flowers are 7 + 7 = 14.
Each flower has 3 petals.
The number of petals is 14 x 3 = 42.
Therefore there are 42 petals.
Question 14.
Henry, Jaime, and Kayla each had 3 snacks packed in their lunch boxes. They each ate one snack in the morning. How many snacks are left in all?
Answer:
The Henry, Jaime, and Kayla each had 3 snacks packed in their lunch boxes.
The total number snacks packed is 3 x 3 = 9.
They each ate one snack in the morning.
They total eaten is 3.
Therefore the number of snack they left is 9 – 3 = 6.
They lifted 6 snacks.
Question 15.
Mathematical PRACTICE Use Algebra Lynn bought some party favors. The price of each party favor was $3. Her total came to $12. How many party favors did Lynn buy? Write a multiplication sentence with a symbol for the unknown. Solve for the unknown.
Answer:
Given that,
The price of each party favor was $3.
Her total came to $12.
The number of party favors did Lynn buy is $3 x $4 = $12.
The Multiplication sentence is $3 x $4 = $12.
$4 x $3 = $12.
The unknown factor is $4.
HOT Problems
Question 16.
Mathematical PRACTICE Look for a Pattern Look at the multiplication table. Color the row of products of the 3s facts. Tell what pattern you see.
Answer:
The factors of 3 are 1 and 3.
The product of factor 3 is 1 x 3 = 3.
Question 17.
Building on the Essential Question How can a number line help you multiply by 3?
Answer:
The number line help to multiply by 3 is skips of 3 and skips of 4 on the number line to help them to multiply by 3 and 4.
Know it is 3 x 4 = 12.
McGraw Hill My Math Grade 3 Chapter 7 Lesson 1 My Homework Answer Key
Practice
Draw an array for each. Then write two multiplication sentences.
Question 1.
3 rows of 8
Answer:
The array of 3 rows of 8 is
The two multiplication sentence is
3 x 8 = 24.
8 x 3 = 24
Question 2.
6 rows of 3
Answer:
The array of 6 rows of 3 is
The two multiplication sentence is
6 x 3 = 18.
3 x 6 = 18.
Multiply. Use the number line to skip count if needed.
Question 3.
5 × 3 = ______________
Answer:
Multiplication of 5 with 3 then you get 15.
5 x 3 = 15.
Question 4.
8 × 3 = _______________
Answer:
Multiplication of 8 with 3 then you get 24.
8 x 3 = 24.
Question 5.
7 × 3 = _______________
Answer:
Multiplication of 7 with 3 then you get 21.
7 x 3 = 21.
Question 6.
4 × 3 = ________________
Answer:
Multiplication of 4 with 3 then you get 12.
4 x 3 = 12.
Algebra Find the unknown factor. Use the Commutative Property.
Question 7.
× 3 = 30
3 × = 30
The unknown is _____________.
Answer:
We know that
10 x 3 = 30
3 x 10 = 30
It is a commutative property of multiplication.
The unknown factor is 10.
Question 8.
3 × = 18
× 3 = 18
The unknown is _____________.
Answer:
We know that,
3 x 6= 18.
8 x 3 = 18.
It is a commutative property of multiplication.
The unknown factor is 6.
Problem Solving
Write a multiplication sentence with a symbol for the unknown for Exercises 9 and 10. Then solve.
Question 9.
A box of popcorn costs S3 at the baseball game. The vendor sells 5 boxes to people in row 22. How much money did the vendor collect for the popcorn?
Answer:
Given that,
A box of popcorn costs is $3 at the baseball game.
The vendor sells 5 boxes to people in row 22.
The money did the vendor collects for the popcorn is $3 x 5 = $15.
Therefore the money they collects for the popcorn is $15.
Question 10.
Gloria has a study guide for her math, social studies, and science classes. Each study guide is 7 pages. How many pages of study guides does Gloria have in all?
Answer:
There are 3 study guides.
Each study guide is 7 pages.
The number of pages in the study guides is 3 x 7 = 21.
Therefore the number of pages that Gloria have in all is 21.
Question 11.
Mathematical PRACTICE Make Sense of Problems Meredith feeds her 3 dogs twice a day. How many times does she feed the dogs in 3 days?
Answer:
Given that,
Meredith feeds her 3 dogs twice a day.
For 3 dogs equal to 6 times.
The number of times that she feed the dogs in 3 days is 3 x 6 = 18.
Therefore the number of times does she feeds the dogs for 3 days is 18 times.
Test Practice
Question 12.
There are 3 rows of cars in the parking lot. Each row has 5 cars. How many cars are in the parking lot?
(A) 18 cars
(B) 15 cars
(C) 12 cars
(D) 9 cars
Answer:
Given that,
There are 3 rows of cars in the parking lot.
Each row has 5 cars.
The number of cars in the parking lot is 3 x 5 = 15.
Option B is the correct answer.