All the solutions provided in McGraw Hill Math Grade 4 Answer Key PDF Chapter 4 Lesson 5 Multiply by a Two-Digit Number will give you a clear idea of the concepts.
McGraw-Hill My Math Grade 4 Answer Key Chapter 4 Lesson 5 Multiply by a Two-Digit Number
Math in My World
Example 1
Ann’s mom buys two helmets. Each helmet costs $24. How much does she spend on helmets?
You need to find 2 × $24.
Multiply.
Multiply the ones.
2 × 4 ones = ___ ones
Multiply the tens.
2 × 2 tens = ___ tens
So, Ann’s mom spends ___
Helpful hint
Line up the factors by the ones place.
Check for Reasonableness
The area model shows the partial products.
So, the answer is correct.
You can estimate to check for reasonableness.
Answer:
Given that,
Ann’s mom buys two helmets.
Each helmet costs $24.
Multiply the ones.
2 × 4 ones = 8 ones.
Multiply the tens
2 × 2 tens = 4 tens.
So, Ann’s mom spends 48.
Using the partial products.
Example 2.
Thirty-one bikes were ordered from Jimmy’s Bike Shop. Each bike has two tires. How many tires will Jimmy need for the bikes?
Estimate 31 × 2 → ____ × ___ = ____
1. Multiply the ones.
2 × 1 one = 2 ones
Write the product in the ones place.
2. Multiply the tens.
2 × 3 tens = 6 tens
Write the product in the tens place.
So, Jimmy will need _____ bike tires.
Check for Reasonableness
The product, ___, is close to the estimate, ____
Answer:
Thirty-one bikes were ordered from Jimmy’s Bike Shop.
Each bike has two tires.
31 x 2 = 62.
Multiply the ones.
2 × 1 one = 2 ones
Write the product in the ones place.
Multiply the tens.
2 × 3 tens = 6 tens
Write the product in the tens place.
So, Jimmy will need 62 bike tires.
The product 62 and it is close to the estimate 60.
Talk Math
Suppose you found 99 as the product of 33 × 3. How can you check to see if your answer is reasonable?
Answer:
Multiplication of 33 with 3 then you get 99.
33 x 3 = 99.
Yes the answer is reasonable.
Guided Practice
Multiply. Check for reasonableness.
Question 1.
Answer:
Multiply the ones.
2 × 2 one = 4 ones.
Write 4 in the ones place.
Multiply the tens.
2 × 4 tens = 8 tens
Write 8 in the tens place.
Therefore the product is 84.
Question 2.
Answer:
Multiply the ones.
3 × 1 one = 3 ones.
Write 3 in the ones place.
Multiply the tens.
3 × 2 tens = 6 tens
Write 6 in the tens place.
Therefore the product is 63.
Question 3.
11 × 4 = ____
Answer:
Multiply the ones.
4 × 1 one = 4 ones.
Write 4 in the ones place.
Multiply the tens.
4 × 1 tens = 4 tens
Write 4 in the tens place.
Therefore the product is 44.
Question 4.
32 × 2 = ____
Answer:
Multiply the ones.
2 × 2 one = 4 ones.
Write 4 in the ones place.
Multiply the tens.
2 × 3 tens = 6 tens
Write 6 in the tens place.
Therefore the product is 64.
Independent Practice
Multiply. Check for reasonableness.
Question 5.
Answer:
Multiply the ones.
2 × 4 one = 8 ones.
Write 8 in the ones place.
Multiply the tens.
2 × 4 tens = 8 tens
Write 8 in the tens place.
Therefore the product is 88.
Question 6.
Answer:
Multiply the ones.
4 × 1 one = 4 ones.
Write 4 in the ones place.
Multiply the tens.
4 × 2 tens = 8 tens
Write 8 in the tens place.
Therefore the product is 84.
Question 7.
Answer:
Multiply the ones.
2 × 3 one = 6 ones.
Write 6 in the ones place.
Multiply the tens.
2 × 1 tens = 2 tens
Write 2 in the tens place.
Therefore the product is 26.
Question 8.
41 × 22 = ___
Answer:
Multiplication of 41 with 22 then you get 902.
41 x 22 = 902.
Algebra Find each unknown number.
Question 11.
41 × 2 = h
h = ____
Answer:
Multiplication of 41 with 2 then you get 82.
41 x 2 = 82.
h = 82.
Therefore the unknown is 82.
Question 12.
12 × 3 = j
j = ____
Answer:
Multiplication of 12 with 3 then you get 36.
12 x 3 = 36.
j = 36.
Therefore the unknown is 36.
Question 13.
4 × 22 = k
k = ___
Answer:
Multiplication of 4 with 22 then you get 88.
4 x 22 = 88.
k = 88.
Therefore the unknown is 88.
Problem Solving
Question 14
Mathematical PRACTICE 1 Plan Your Solution A city has 23 swing sets. Each has 3 swings. How many swings are there in all?
Answer:
Given that,
A city has 23 swing sets. Each has 3 swings.
Multiplication of 23 with 3 then you get 69.
23 x 3 = 69.
Therefore there are 69 wings in all.
Question 15.
The world’s largest rodent is called a capybara. It can weigh 34 kilograms. How much could 2 capybaras weigh?
Answer:
Given that,
It can weigh 34 kilograms.
How much could 2 capybaras weigh.
So, 34 x 2 = 68.
Therefore the 2 capybaras weigh is 68 kilograms.
Question 16.
Recycling one ton of paper saves 17 trees. About how many trees are saved if 4 tons of paper are recycled?
Answer:
Given that,
Recycling one ton of paper saves 17 trees.
The trees are saved if 4 tons of paper are recycled is 17 x 4 = 68.
Therefore 68 trees are saved if 4 tons of paper are recycled.
HOT Problems
Question 17.
Mathematical PRACTICE 6 Explain to a Friend Adrian has four boxes of action figures. There are 12 in each box. Alec has 21 action figures in each of his three boxes. Who has more action figures? Explain to a friend.
Answer:
Given that,
Adrian has four boxes of action figures.
There are 12 in each box.
The number of action figures in four boxes are 12 x 4 = 48.
Alec has 21 action figures in each of his three boxes.
The number of action figures in 3 boxes are 21 x 3 = 63.
63 is greater than 48.
Therefore Alec has more action figures.
Question 18.
? Building on the Essential Question How can estimation be used to check multiplication problems for reasonableness?
Answer:
We can use estimation to check multiplication problems for reasonableness. Because it gives the round about. It answer should be close to the correct one.
McGraw Hill My Math Grade 4 Chapter 4 Lesson 5 My Homework Answer Key
Practice
Multiply. Draw an area model. Check for reasonableness.
Question 1.
Answer:
Multiplication of 30 with 2 then you get 60.
30 x 2 = 60.
The area model of 30 x 2 is
Multiplication of 30 with 0 equal to 0.
Multiplication of 30 with 2 then you get 60.
Add the products 0 + 60 = 60.
Therefore the product is 60.
Question 2.
Answer:
Multiplication of 21 with 4 then you get 84.
21 x 4 = 84.
The area model of 21 x 4.
Multiplication of 4 with 20 then you get 80.
Multiplication of 4 with 1 then you get 4.
Add the products 80 + 4 = 84.
Therefore the product is 84.
Question 3.
Answer:
Multiplication of 86 with 1 then you get 86.
86 x 1 = 86.
The area model of 86 x 1 is
Multiplication of 1 with 80 then you get 80.
Multiplication of 1 with 6 then you get 6.
Add the products 80 + 6 = 86.
Therefore the product is 86.
Multiply.
Question 4.
3 × 31 = ____
Answer:
Multiplication of 3 with 31 then you get 93.
3 x 31 = 93.
Question 5.
6 × 11 = ____
Answer:
Multiplication of 6 with 11 then you get 66.
6 x 11 = 66.
Problem Solving
Question 6.
Caroline makes $3 an hour pet-sitting for the neighbors. Last summer she worked 23 hours. How much money did Caroline earn?
Answer:
Given that,
Caroline makes $3 an hour pet-sitting for the neighbors.
Last summer she worked 23 hours.
The money did Caroline earn is $3 x 23 = $69.
Therefore the Caroline earn is $69.
Question 7.
Simon has 12 CDs. He burns 3 copies of each. How many CDs did Simon make?
Answer:
Given that,
Simon has 12 CDs.
He burns 3 copies of each.
So, 12 x 3 = 36.
Therefore the number of CDs did Simon make is 36.
Question 8.
The school cafeteria has 4 rows of tables. Each row has 22 seats. How many students can sit in the school cafeteria at the same time?
Answer:
Given that,
The school cafeteria has 4 rows of tables.
Each row has 22 seats.
So, 4 x 22 = 88.
Therefore the students sit in the school cafeteria at the same time is 88.
Question 9.
Mathematical PRACTICE 2 Use Number Sense Steve is playing a memory game with picture cards. He makes 5 rows and puts 11 cards in each row. How many picture cards is Steve using in this game?
Answer:
Given that,
He makes 5 rows and puts 11 cards in each row.
The cards used in game is 5 x 11 = 55.
Therefore 55 picture cards is used in this game by Steve.
Test Practice
Question 10.
John wants to buy birthday gifts for 4 friends. He can spend $20 for each gift. How much money can John spend on gifts in all?
A. $80
B. $40
C. $34
D. $24
Answer:
Given that,
John wants to buy birthday gifts for 4 friends.
He can spend $20 for each gift.
John spend on gifts is 4 x $20 = $80.
Option A is the correct answer.