# Texas Go Math Grade 4 Lesson 8.6 Answer Key Choose a Multiplication Method

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## Texas Go Math Grade 4 Lesson 8.6 Answer Key Choose a Multiplication Method

Essential Question

How can you find and record products of two 2-digit numbers?
To find the product of two double-digit number,
place ones in the ones column and tens in the tens column.
Underneath that we make another
two digit number and then we add.
Explanation:
For Example, Unlock the Problem

• Underline the sentence that tells you how to find the answer.
• Circle the numbers you need to use. What operation will you use?

Did you know using math can help prevent you from getting a sunburn?

The time it takes to burn without sunscreen multiplied by the SPF, or sun protection factor, is the time you can stay in the sun safely with sunscreen.

If today’s UV index is 8, Erin will burn in 15 minutes without sunscreen. If Erin puts on lotion with an SPF of 25, how long will she be protected?

One Way Use partial products to find 15 × 25. Explanation: Draw a Picture to check your work. Explanation:
25 x 15 = 375 Math Talk

Mathematical Processes
The product is 375. Explain what 375 means for Erin.
375 for Erin means the time it takes to burn without sunscreen multiplied by the SPF, or sun protection factor, is the time you can stay in the sun safely with sunscreen.

Another Way Use regrouping to find 15 × 25.

Estimate. 20 × 20 = __________
20 x 20 = 400

STEP 1
Think of 15 as 1 ten 5 ones.
Multiply 25 by 5 ones, or 5. STEP 2
Multiply 25 by 1 ten, or 10. STEP 3 Share and Show

Question 1.
Find the Product. Explanation: Math Talk

Mathematical Processes
Explain why you begin with the ones place when you use the regrouping method to multiply.
Regrouping can be defined as the process of making groups of tens when carrying out operations like addition, subtraction, multiplication and division with two-digit numbers or larger.
To regroup means to rearrange groups in place value to carry out an operation.

Estimate. Then choose a method to find the product.

Question 2.
Estimate: ___________ Estimate:525
Explanation:
Estimates of 36 is 35 and 14 is 15
35 x 15 Question 3.
Estimate: ___________ Estimate:2400
Explanation:
Estimates of 63 is 60 and 42 is 40
60 x 40 Question 4.
Estimate: ___________ Estimate: 4250
Explanation:
Estimates of 84 is 80 and 53 is 50 Question 5.
Estimate: ___________ Estimate: 1050
Explanation:
Estimates of 71 is 70 and 13 is 15
70 x 15 Problem Solving

Practice: Copy and Solve Estimate. Find the product.

Question 6.
29 × $82 Answer: 2,378 Estimate: 2400 Explanation: Estimates of 29 is 30 and 82 is 80 30 x 80 Question 7. 57 × 79 Answer: 4,503 Estimate: 4400 Explanation: Estimates of 57 is 55 and 79 is 80 55 x 80 Question 8. 80 × 27 Answer: 2,160 Estimate: 2000 Explanation: Estimates of 27 is 25 80 x 25 Question 9. 32 ×$ 75
Estimate: 2250
Explanation:
Estimate of 32 is 30
30 x 75 H.O.T. Algebra Use mental math to find the number.

Question 10.
30 × 14 = 420, so 30 × 15 = ___________ .
30 x 15 = 450
(30 x 10) + (30 x 5) = 300 + 150 = 450
Explanation:
Mental math techniques helps to convert complex multiplication into simpler multiplications and use addition and subtraction to save time.
If you observe in the above equation, 30 is common multiplicand
and in multiplier 1 number is added
So, when multiplier is increased product also increases by multiplicand.

Question 11.
25 × 12 = 300, so 25 × ___________ = 350.
25 × 14 = 350
Explanation:
Mental math techniques helps to convert complex multiplication into simpler multiplications and use addition and subtraction to save time.
If you observe in the above equation, 25 is common multiplicand
and product increased by 50
So, when product is increased by 50 every time the multiplier also increased by 2
So, 12 + 2 = 14 (Multiplier).

Unlock the Problem

Question 12. H.O.T. Multi-Step Apply Martin collects stamps. He counted 48 pages in his collector’s album. The first 20 pages each have 35 stamps in 5 rows. The rest of the pages each have 54 stamps. How many stamps does Martin have in his album? a. What do you need to know?
Martin need to find total number of stamps his Album.

b. How will you use multiplication to find the number of stamps?
Using partial 2-digit method to find the product.

c. Tell why you might use addition and subtraction to help solve the problem.
Addition is used to know the total number of stamps in album.
Subtraction is used to find the rest of the pages.

d. Show the steps to solve the problem.
The following are the steps:
Martin counted 48 pages in his collector’s album.
The first 20 pages each have 35 stamps in 5 rows.
Total stamps in 20 pages
20 x 35 x 5 = 3,500 stamps
Rest of the pages 48 – 20 = 28
The rest of the pages each have 54 stamps.
54 x 28 = 1,512 stamps
Total stamps Martin have in his album
3,500 + 1,512 = 5,012 stamps.

e. Complete the sentences.
Martin has a total of ____________ stamps on the first 20 pages.
There are ____________ more pages after the first 20 pages in Martin’s album.
There are ____________ stamps on the rest of the pages.
There are ____________ stamps in the album.
Martin has a total of 3,500 stamps on the first 20 pages.
There are 28 more pages after the first 20 pages in Martin’s album.
There are 1,512 stamps on the rest of the pages.
There are 5,012 stamps in the album.

Question 13.
H.O.T. Multi-Step One group of 15 students read for 30 minutes. Another group of 25 students read for 45 minutes. How many minutes did the students spend reading? Explain.
75 minutes or 1 hr 15 min.
Explanation:
One group of 15 students read for 30 minutes.
Another group of 25 students read for 45 minutes.
Total minutes spent by the students on reading
30 + 45 = 75 minutes or 1 hr 15 min.

Question 14.
When a cheetah runs, its stride is 22 feet long. What distance does the cheetah run in 45 strides?
(A) 980 feet
(B) 990 feet
(C) 198 feet
(D) 99 feet
Option(B)
Explanation:
When a cheetah runs, its stride is 22 feet long.
Total distance the cheetah run in 45 strides
45 x 22 = 990 feet

Question 15.
Student tickets to a theme park cost $27. How much do 32 student tickets cost? (A)$810
(B) $854 (C)$864
(D) $288 Answer: Option(C) Explanation: Student tickets to a theme park cost$27.
Cost of 32 student tickets 32 x 27 = 864

Question 16.
Multi-Step A theater has 52 rows of 26 seats. There are people sitting in 241 seats. How many seats are empty?
(A) 175 seats
(B) 111 seats
(C) 1,101 seats
(D) 1,111 seats
Option(D)
Explanation:
A theater has 52 rows of 26 seats.
Total seats 52 x 26 = 1,352
There are people sitting in 241 seats.
Number of seats empty are 1,352 – 241 = 1,111

TEXAS Test Prep

Question 17.
Each row of peach trees has 37 trees. There are 16 rows. How many peach trees are there?
(A) 53
(B) 259
(C) 592
(D) 342
Option(C)
Explanation:
Each row of peach trees has 37 trees.
There are 16 rows.
Number of peach trees 37 x 16 = 592

### Texas Go Math Grade 4 Lesson 8.6 Homework and Practice Answer Key

Estimate. Then choose a method to find the product.

Question 1.
Estimate Estimate: 525
Explanation:
Estimates of 34 is 35 and 16 is 15
35 x 15 Question 2.
Estimate Estimate: 1000
Explanation:
Estimates of 49 is 50 and 21 is 20
50 x 20 Question 3.
Estimate Estimate: 3300
Explanation:
Estimates of 62 is 60
60 x 55 Problem Solving

A coach bought 56 items at the sports shop. He got 18 footballs for $32 each. The rest of the items were shoulder pads that cost$89 each. How much did the coach spend for the 56 items?

Question 4.
What do you need to know?
Need to find the total amount spent by the coach on 56 items at the sports shop.

Question 5.
How will you use multiplication to find the total cost?
Using partial method of 2-digit multiplication.

Question 6.
Tell why you might use addition and subtraction to solve the problem.
Addition is used to find the total cost of 56 items.
Subtraction is used to know how many shoulder pads coach purchased.

Question 7.
Show the steps to solve the problem.
A coach bought 56 items at the sports shop.
He got 18 footballs for $32 each. 18 x 32 = 576 The rest of the items were shoulder pads that cost$89 each.
Total shoulder pads 56 – 18 = 38
Total cost of shoulder pads 38 x 89 = 3,382
Total amount spent for the 56 items by coach
576 + 3382 = 3,958

Question 8.
Complete the sentences.
The coach spent _________ for footballs.
The coach bought _________ shoulder pads.
The coach spent _________ shoulder pads.
The coach spent a total of _________.
The coach spent 18 for footballs.
The coach bought 38 shoulder pads.
The coach spent 3,382 shoulder pads.
The coach spent a total of 3,958.

Lesson Check

Question 9.
A beach clean-up crew filled 34 garbage -cans with litter. Each garbage can holds 55 gallons. How many gallons of garbage did the crew pick up?
(A) 1,770 gallons
(B) 1,670 gallons
(C) 1,650 gallons
(D) 1,870 gallons
Option(D)
Explanation:
A beach clean-up crew filled 34 garbage -cans with litter.
Each garbage can holds 55 gallons.
Total gallons of garbage the crew pick up
34 x 55 = 1,870

Question 10.
Folding chairs cost $27 each. How much do 72 folding chairs cost? (A)$1,844
(B) $1,944 (C)$1,954
(D) $1,934 Answer: Option(B) Explanation: Folding chairs cost$27 each.
Cost of 72 folding chairs 72 x 27 = 1,944

Question 11.
There are 13 volunteers at the community garden. Each person works 15 hours a week. How many hours are spent working at the garden each week?
(A) 215 hours
(B) 185 hours
(C) 195 hours
(D) 205 hours
Option(C)
Explanation:
There are 13 volunteers at the community garden.
Each person works 15 hours a week.
Number of hours spent work at the garden each week
13 x 15 = 195 hours

Question 12.
There are 25 paper plates in a package. Karen bought 20 packages. How many paper plates did Karen buy?
(A) 400
(B) 500
(C) 250
(D) 550
Option(B)
Explanation:
There are 25 paper plates in a package.
Karen bought 20 packages.
Number of paper plates Karen bought
25 x 20 = 500

Question 13.
Multi-Step The town conservation manager bought 16 maple trees for $26 each. She paid with five$100 bills. How much change will the manager receive?

(A) $84 (B)$416
(C) $94 (D)$184
Option(A)
Explanation:
The town conservation manager bought 16 maple trees for $26 each. Cost of 16 maple = 26 x 16 = 416 She paid with five$100 bills.
500 – 416 = \$84

Question 14.
Multi-Step Section A of a stadium has 42 rows with 56 seats in each row. Section B has 64 rows with 54 seats in each row. If the stadium sells tickets for all the seats in both sections, how many tickets are sold?
(A) 5,498
(B) 5,808
(C) 5,608
(D) 5,698