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## Texas Go Math Grade 3 Lesson 4.2 Answer Key Estimate Sums

**Unlock the Problem**

The table shows how many dogs went to Pine Lake Dog Park during the summer months. About how many dogs went to the park during June and August?

You can estimate to find about how many or about how much. An estimate is a number close to an exact amount.

**One Way** Use compatible numbers.

Compatible numbers are numbers that are easy to compute mentally and are close to the real numbers.

So, about ________ dogs went to Pine Lake Dog Park during June and August.

Answer: 900

Explanation:

In the month of June 432 dogs went to park

In the month of August 489 dogs went to park

When they are estimated close to an exact number

425 + 475 = 900

So, about 900 dogs went to Pine Lake Dog Park during June and August.

**Math Talk**

**Mathematical Processes**

Will the sum of the compatible numbers 425 and 475 be greater than or less than the exact sum? Explain.

Answer:

Less then the exact sum

Explanation

425 + 475 = 900

432 + 489 = 921

the sum of the compatible numbers are less than the exact sum

So, 900 < 921

Question 1.

What other compatible numbers could you have used?

Answer:

400 and 500

425 is nearer to 400 rounding to hundred and 475 is rounded to 500

Explanation:

Rounding to nearest hundreds can be used, to compete the numbers.

Question 2.

About how many dogs went to the park during July and August? What compatible numbers could you use to estimate?

Answer: 800

Explanation:

According to the given information,

July month 317 dogs went to park

August month 489 dogs went to the park

The sum of the dogs is 806,

when rounded to nearest hundreds, it is 800

**Another Way** Use place value to round.

432 + 489 = ☐

First, find the place to which you want to round. Round both numbers to the same place. The greatest place value of 432 and 489 is hundreds. Round each number to the nearest hundred.

400 + 500 = 900

Find the sum of the rounded numbers.

400 + 500 = ________

Answer: 900

Explanation:

432 is rounded to the nearest hundred as 400

489 is rounded to the hundred as 500

So, 400 + 500 = 900

**Math Talk**

**Mathematical Processes**

How would you round 432 and 489 to the nearest ten? What would be the estimated Explain?

Answer:

430 and 490

Explanation:

432 is rounded to nearest hundred is 430 and

489 is rounded to nearest hundred is 490

**Share and Show**

**Estimate the sum.**

Question 1.

Use compatible numbers.

Answer:

Explanation:

The numbers which are close to the actual numbers, and can be easily added, subtracted or divided orally are known as compatible numbers.

47 is rounded to nearest tens 50 and

23 is rounded to nearest tens 25

Question 2.

Use rounding.

Answer:

Explanation:

The numbers which are close to the actual numbers, and can be easily added, subtracted or divided orally are known as compatible numbers.

304 is rounded to nearest hundred as 300

494 is rounded to nearest hundred as 500

**Use rounding or compatible numbers to estimate the sum.**

Question 3.

Answer:

Explanation:

The numbers which are close to the actual numbers, and can be easily added, subtracted or divided orally are known as compatible numbers.

Estimates means rounding to the nearest tens or hundreds.

421 can be estimated to a compatible number 420 and

218 can be written as 220 to nearest ten, then

the sum of the 420 + 220 = 640

Question 4.

Answer:

Explanation:

The numbers which are close to the actual numbers, and can be easily added, subtracted or divided orally are known as compatible numbers.

Estimates means rounding to the nearest tens or hundreds.

369 can be estimated to a compatible number 370 and

480 is exactly rounded to its tens,

So, the sum of the 370 + 480 = 850

Question 5.

Answer:

Explanation:

The numbers which are close to the actual numbers, and can be easily added, subtracted or divided orally are known as compatible numbers.

Estimates means rounding to the nearest tens or hundreds.

27 can be estimated to a compatible number 25 and

78 can be written as 80 to nearest ten, then

the sum of the 25 + 80 = 105

Question 6.

Answer:

Explanation:

The numbers which are close to the actual numbers, and can be easily added, subtracted or divided orally are known as compatible numbers.

Estimates means rounding to the nearest tens or hundreds.

267 can be estimated to a compatible number 300 and

517 can be written as 500 to nearest hundred, then

the sum of the 300+ 500 = 800

Question 7.

Answer:

Explanation:

The numbers which are close to the actual numbers, and can be easily added, subtracted or divided orally are known as compatible numbers.

Estimates means rounding to the nearest tens or hundreds.

465 can be estimated to a compatible number 470 and

478 can be written as 480 to nearest ten, then

the sum of the 470 + 480 = 950

Question 8.

Answer:

Explanation:

The numbers which are close to the actual numbers, and can be easily added, subtracted or divided orally are known as compatible numbers.

Estimates means rounding to the nearest tens or hundreds.

278 can be estimated to a compatible number 280 and

369 can be written as 370 to nearest ten, then

the sum of the 280 + 370 = 650

**Problem Solving**

Question 9.

**Multi-Step** Green Lawn Service ordered 186 bags of top soil and 462 bags of fertilizer. Estimate to the nearest hundred how many bags Green Lawn Service ordered.

Justify your answer.

Answer:

Explanation:

Green Lawn Service ordered 186 bags of top soil and

462 bags of fertilizer.

estimating to the nearest hundred

186 is rounded to 200 and 462 to 500

So, 200 + 500 = 700

**Problem Solving**

**Use the table for 10-13.**

Question 10.

About how many pet bowls were sold in June and July altogether?

Answer:

148 pet bowls

Explanation:

pet bowls sold in the month of June = 91,

pet bowls sold in the month of July = 57

total pet bowls sold in both the months

91 + 57 = 148

Question 11.

**H.O.T.** What’s the Question? The answer is about 800.

Answer:

How much bags of pet food sold in the month June and July together? rounded nearest hundred?

Explanation:

Pet food sold in the month of June 419 and

Pet food sold in the month of July 370

Total food sold in both the months

419 + 370 = 789

when rounded to nearest hundreds

400 + 400 = 800

Question 12.

**H.O.T. Multi-Step** Dan estimated the lowest monthly sales of both pet bowls and bags of pet food to be about 300. What month had the lowest sales? Explain.

Answer: August

Explanation:

From the above table the least sales month is August

The sales of pet bowls is 76

The sales of pet food bag is 228

the sum of pet bowl and bag of pet food

76 + 228 = 304

304 is rounded to 300

Question 13.

**H.O.T. Multi-Step** Dan said the total number of bags of pet food sold in June, July, and August was about 1,000. How did Dan estimate? Explain.

Answer: 1017

Explanation:

bags of pet food sold in June, July, and August

419 + 370 + 228 = 1017

1017 rounding to 1000, as 1017 is nearer to 1000

**Daily Assessment Task**

**Fill in the bubble for the correct answer choice.**

Question 14.

**Use Tools** The table shows the number of steps from bottom to top for each pyramid. Which of these statements shows the best estimate of how many steps there are in both pyramids?

(A) 5 + 100 = 105

(B) 0 + 75 = 75

(C) 10 + 90 = 100

(D) 6 + 95 = 101

Answer:

Option (C)

Explanation:

Number of steps in Djoser is 6

Number of steps in Chichen Itza is 91

The sum of both pyramids

6 + 91 = 97

write the estimates of both the sums

10 + 90 = 100

as 97 can be rounded to 100

Question 15.

Lea and Josh used sugar cubes to build a model of a pyramid. First, they glued 196 cubes to make a square base. Next, they used 144 cubes to make the first step. Which is the best estimate of the number of sugar cubes Lea and Josh used to build the first two steps of their pyramid?

(A) 440

(B) 300

(C) 220

(D) 400

Answer:

Option (B)

Explanation:

First, they glued 196 cubes to make a square base.

Next, they used 144 cubes to make the first step.

The best estimate of the number of sugar cubes Lea and Josh used to build the first two steps of their pyramid

196 + 144 = 340

Estimating to compatible number 300

Question 16.

**Multi-Step** The height of the Great Pyramid of Giza is about 481 feet. The length of one side of its base is 755 feet. What is the best estimate of the sum of the height and length?

(A) 1,000 feet

(B) 1,100 feet

(C) 1,300 feet

(D) 1,500 feet

Answer:

Option (B)

Explanation:

The height of the Great Pyramid of Giza is about 481 feet.

The length of one side of its base is 755 feet.

The sum of both pyramids

481 + 755 = 1,236

The best estimate of the sum of the height and length 1,100

**Texas Test Prep**

Question 17.

Tracy ordered 325 toys and 165 bags of food for her new pet store. Which is the best estimate of the total number of items Tracy ordered?

(A) 700

(B) 500

(C) 400

(D) 600

Answer:

Option (B)

Explanation:

Tracy ordered 325 toys and 165 bags of food for her new pet store.

The best estimate of the total number of items Tracy ordered

325 + 165 = 300 + 200 = 500

### Texas Go Math Grade 3 Lesson 4.2 Homework and Practice Answer Key

**Use rounding or compatible numbers to estimate the sum.**

Question 1.

18 + 53

Answer:

20 + 50 = 70

Explanation:

The numbers which are close to the actual numbers, and can be easily added, subtracted or divided orally are known as compatible numbers.

18 is rounded to nearest ten as 20

53 is rounded to nearest ten as 50

Question 2.

37 + 52

Answer:

40 + 50 = 90

Explanation:

The numbers which are close to the actual numbers, and can be easily added, subtracted or divided orally are known as compatible numbers.

37 is rounded to nearest ten as 40

52 is rounded to nearest ten as 50

Question 3.

345 + 213

Answer:

350 + 200 = 550

Explanation:

The numbers which are close to the actual numbers, and can be easily added, subtracted or divided orally are known as compatible numbers.

345 is rounded to nearest ten as 350

213 is rounded to nearest ten as 200

Question 4.

509 + 478

Answer:

500 + 480 = 980

Explanation:

The numbers which are close to the actual numbers, and can be easily added, subtracted or divided orally are known as compatible numbers.

509 is rounded to nearest ten as 500

478 is rounded to nearest ten as 480

Question 5.

542 + 212

Answer:

540 +210 = 750

Explanation:

The numbers which are close to the actual numbers, and can be easily added, subtracted or divided orally are known as compatible numbers.

542 is rounded to nearest ten as 540

212 is rounded to nearest ten as 210

Question 6.

109 + 688

Answer:

100 + 700 = 800

Explanation:

The numbers which are close to the actual numbers, and can be easily added, subtracted or divided orally are known as compatible numbers.

109 is rounded to nearest hundred as 100

688 is rounded to nearest hundred as 700

**Problem Solving**

Question 7.

Seth bought a pair of sneakers for $48 and a jacket for $64. Explain how you can estimate to find the total amount that he spent for the sneakers and jacket.

Answer: $112

Explanation:

Seth bought a pair of sneakers for $48 and a jacket for $64.

the total amount that he spent for the sneakers and jacket.

$48 + $64 = $112

$112 can be rounded to $110 as compatible number to estimate.

Question 8.

Elena drove 245 miles last week and 222 miles this week. She estimated that she drove about 475 miles in both weeks. How did Elena estimate?

Answer:

467 can be rounded to 475 as compatible number to estimate

Explanation:

Elena drove 245 miles last week and 222 miles this week.

She estimated that she drove about 475 miles in both weeks.

245 + 222 = 467

467 can be rounded to 475 as compatible number to estimate.

**Lesson Check**

**Fill in the bubble completely to show your answer.**

Question 9.

Cal has $42. He gets $25 from his grandparents for his birthday. Which of these statements shows the best estimate of the amount of money Cal has now?

(A) $50 + $30 = $80

(B) $50 + $20 = $70

(C) $40 + $40 = $80

(D) $40 + $25 = $65

Answer:

Option (B)

Explanation:

Cal has $42.

He gets $25 from his grandparents for his birthday.

Total amount Cal has now

42 + 25 = 67

the best estimate of the amount of money Cal has now

67 can be rounded to 70 as compatible number to estimate.

Question 10.

Mr. Avery’s class made $118 for the fundraiser. Mrs. Bolero’s class made $189 for the fundraiser. Which of these statements shows the best estimate of the total amount both classes raised?

(A) $100 + $200 = $300

(B) $125 + $150 = $275

(C) $100 + $100 = $200

(D) $200 + $200 = $400

Answer:

Option (A)

Explanation:

Mr. Avery’s class made $118 for the fundraiser.

Mrs. Bolero’s class made $189 for the fundraiser.

The total amount of both classes raised

118 + 189 = 307

the best estimate of the total amount both classes raised

307 can be rounded to 300 as compatible number to estimate

Question 11.

Which is the best estimate of the total number of students in kindergarten and first grade at Wayside Elementary School?

(A) 350

(B) 300

(C) 400

(D) 500

Answer:

Option (C)

Explanation:

Number of students in Kindergarten = 187

Number of students in First grade = 203

The sum of the two classes

187 + 203 = 390

390 can be rounded to 400 as compatible number to estimate

Question 12.

**Multi-Step** Which is the best estimate of the total number of students in second, third, and fourth grade at Wayside Elementary School?

(A) 500

(B) 400

(C) 700

(D) 800

Answer:

Option (D)

Explanation:

Students in Second class= 382

Students in Third class = 238

Students in Forth class = 178

Sum of 3 grades

382 + 238 + 178 = 798

798 can be rounded to 800 as compatible number to estimate

Question 13.

**Multi-Step** Which is the best estimate of the total number of students in all grades at Wayside Elementary School?

(A) 900

(B) 1,200

(C) 1,100

(D) 1,000

Answer:

Option (B)

Explanation:

Students in Kindergarten = 187

Students in First grade = 203

Students in Second class= 382

Students in Third class = 238

Students in Forth class = 178

the sum of all grade students in the Wayside Elementary school

187 + 203 + 382 + 238 + 178 = 1188

1188 can be rounded to 1200 as compatible number to estimate