## Envision Math 4th Grade Textbook Answer Key Topic 2 Reteaching

**Reteaching**

**Set A, pages 24-25**

Use a number line to round 837 to the nearest ten.

Compare 837 to the halfway point, which is 835.

837 is to the right of the halfway point. So, 837 rounds to 840.

Remember to use the midpoint of the number line as a guide for rounding.

Use a number line to round each number to the place of the underlined digit.

Question 1.

3,__7__67

Answer:

Question 2.

2,5__1__5

Answer:

Question 3.

4__3__4

Answer:

Question 4.

6,__7__24

Answer:

Question 5.

1,6__2__3

Answer:

Question 6.

4,__2__93

Answer:

Question 7.

5,__1__93__
__Answer:

Question 8.

__9__26

Answer:

Question 9.

__4__67

Answer:

Question 10.

8,4__2__7

Answer:

**Set B, pages 26–27**

Round 346,764,802 to the nearest hundred thousand.

The digit to the right of the rounding place is 6.

Since 6 > 5, round by adding 1 to the digit in the hundred thousands place.

So, 346,764,802 rounds to 346,800,000.

Round 28,216 to the nearest thousand.

The digit to the right of the rounding place is 2.

Since 2 < 5, the digit in the rounding place stays the same.

So, 28,216 rounds to 28,000.

Remember to look at the number to the right of the rounding place. Then change the digits to the right of the rounding place to zeros.

Round each number to the place of the underlined digit.

Question 1.

16__6__,742

Answer:

Question 2.

7__6__,532

Answer:

Question 3.

__5__,861

Answer:

Question 4.

2,43__2__,741

Answer:

Question 5.

__1__32,505

Answer:

Question 6.

__2__57,931

Answer:

Question 7.

3__8__,427

Answer:

Question 8.

6,__9__25

Answer:

Question 9.

2__4__3,819

Answer:

Question 10.

__6__93,587

Answer:

Question 11.

15,__1__83,297

Answer:

Question 12.

4__9__3,620,761__
__Answer:

**Set C, pages 28–30**

Add 155 + 83. Use mental math.

Look for a ten and use the breaking apart method. Adding 5 to 155 is easy.

Break apart 83.

155 + 5 = 160

160 + 78 = 238

So, 155 + 83 = 238.

Remember that when you use compensation, you must adjust the sum or difference.

Question 1.

53 + 88

Answer:

Question 2.

372 + 226

Answer:

Question 3.

734 – 223

Answer:

Question 4.

147 – 56

Answer:

Question 5.

5,342 + 1,826

Answer:

Question 6.

283 – 169

Answer:

Question 7.

6,000 + 0

Answer:

Question 8.

854 + 353

Answer:

Question 9.

1,854 + 362

Answer:

Question 10.

3,874 + 121

Answer:

Question 11.

363 + 784

Answer:

Question 12.

841 + 1,024

Answer:

Question 13.

676 – 521

Answer:

Question 14.

1,089 – 961

Answer:

Question 15.

899 – 275

Answer:

Question 16.

1,444 – 1,225

Answer:

Question 17.

2,401 – 1,025

Answer:

Question 18.

2,499 + 2,601

Answer:

**Set D, pages 32–33**

Estimate

Round each number to the nearest hundred.

1,579 rounds to 1,600.

1,248 rounds to 1,200.

Round each number to the nearest ten.

534 rounds to 530.

246 rounds to 250.

Remember that you can round numbers to the nearest hundred or thousand when estimating sums and differences.

Question 1.

473 + 465

Answer:

Question 2.

8,352 – 3,421

Answer:

Question 3.

586 – 483

Answer:

Question 4.

4,094 + 246

Answer:

Question 5.

1,440 – 933

Answer:

Question 6.

748 – 392

Answer:

Question 7.

981 + 193

Answer:

Question 8.

725 + 635

Answer:

Question 9.

318 + 567

Answer:

Question 10.

4,806 – 295

Answer:

Question 11.

743 – 188

Answer:

Question 12.

607 – 492

Answer:

Question 13.

3,593 + 1,208

Answer:

Question 14.

6,921 + 451

Answer:

Question 15.

7,264 – 2,835

Answer:

Question 16.

1,847 + 3,086

Answer:

**Set E, pages 34–35**

What do I know?

Cathy had $8. She bought a sandwich, a fruit cup, and a milk at the snack bar. She spent a total of $6 on the sandwich and milk.

How much did Cathy have left?

What am I asked to find?

The amount of money Cathy had left.

Is there missing information needed to solve the problem?

Yes, I need to know the cost of the fruit cup so I can find the total spent. Then I can find how much Cathy had left.

Is there extra information not needed to solve the problem?

No, there is no extra information.

Remember some problems have information you do not need. Solve.

Question 1.

At the zoo, Doug saw 14 wallabies. He saw 5 Agile wallabies. The rest of the wallabies he saw were Rock wallabies. How many Rock wallabies did Doug see?

Answer:

Question 2.

At the same zoo, Helen went to the Bat House exhibit to look at the Horseshoe bats. Min went to the same exhibit and saw 12 different bats. How many bats did Helen and Min see all together?

Answer:

**Set F, pages 36–38**

Add 359 + 723.

Estimate: 400 + 700 = 1,100

The answer is reasonable.

Remember to regroup if necessary when adding whole numbers.

Question 1.

215 + 8,823

Answer:

Question 2.

14,296 + 444

Answer:

Question 3.

2,417 + 3,573

Answer:

Question 4.

572 + 941

Answer:

Question 5.

Answer:

Question 6.

Answer:

Question 7.

Answer:

Question 8.

**Set G, pages 40–41**

Find 831 – 796.

Estimate: 830 – 800 = 30

The answer is reasonable

Remember you may need to regroup before you subtract.

Question 1.

415 – 323

Answer:

Question 2.

673 – 294

Answer:

Question 3.

186 – 77

Answer:

Question 4.

4,978 – 2,766

Answer:

Question 5.

Answer:

Question 6.

Answer:

Question 7.

Answer:

Question 8.

Answer:

**Set H, pages 42–43**

Find 400 – 378.

Estimate: 400 – 380 = 20

Regroup 4 hundreds to tens and ones.

The answer is reasonable.

Remember to use the inverse operation to check your answer.

Question 1.

700 – 255

Answer:

Question 2.

1,054 – 438

Answer:

Question 3.

320 – 111

Answer:

Question 4.

4,508 – 2,613

Answer:

Question 5.

Answer:

Question 6.

Answer:

**Set J, pages 44–46**

The standard weight of a penny is 2.50 g, a standard nickel is 5.0 g, and a standard half dollar is 11.34 g. Estimate how much greater the weight of a half dollar is than a nickel.

What am I asked to find?

Estimate the difference between the weights.

Use subtraction to solve.

11.34 rounds to 11.

11.0 – 5.0 = 6.0

Remember you can draw a picture or diagram to model the problem.

Question 1.

A 7-kilometer run had markers at the starting line and at the finish line. Markers were placed at each kilometer. How many markers

were used for the race?

Answer: