## 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.
3,767
Answer:

Question 2.
2,515
Answer:

Question 3.
434
Answer:

Question 4.
6,724
Answer:

Question 5.
1,623
Answer:

Question 6.
4,293
Answer:

Question 7.
5,193
Answer:

Question 8.
926
Answer:

Question 9.
467
Answer:

Question 10.
8,427
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.
166,742
Answer:

Question 2.
76,532
Answer:

Question 3.
5,861
Answer:

Question 4.
2,432,741
Answer:

Question 5.
132,505
Answer:

Question 6.
257,931
Answer:

Question 7.
38,427
Answer:

Question 8.
6,925
Answer:

Question 9.
243,819
Answer:

Question 10.
693,587
Answer:

Question 11.
15,183,297
Answer:

Question 12.
493,620,761
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: