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

Question 2.
2,515

Question 3.
434

Question 4.
6,724

Question 5.
1,623

Question 6.
4,293

Question 7.
5,193

Question 8.
926

Question 9.
467

Question 10.
8,427

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

Question 2.
76,532

Question 3.
5,861

Question 4.
2,432,741

Question 5.
132,505

Question 6.
257,931

Question 7.
38,427

Question 8.
6,925

Question 9.
243,819

Question 10.
693,587

Question 11.
15,183,297

Question 12.
493,620,761

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

Question 2.
372 + 226

Question 3.
734 – 223

Question 4.
147 – 56

Question 5.
5,342 + 1,826

Question 6.
283 – 169

Question 7.
6,000 + 0

Question 8.
854 + 353

Question 9.
1,854 + 362

Question 10.
3,874 + 121

Question 11.
363 + 784

Question 12.
841 + 1,024

Question 13.
676 – 521

Question 14.
1,089 – 961

Question 15.
899 – 275

Question 16.
1,444 – 1,225

Question 17.
2,401 – 1,025

Question 18.
2,499 + 2,601

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

Question 2.
8,352 – 3,421

Question 3.
586 – 483

Question 4.
4,094 + 246

Question 5.
1,440 – 933

Question 6.
748 – 392

Question 7.
981 + 193

Question 8.
725 + 635

Question 9.
318 + 567

Question 10.
4,806 – 295

Question 11.
743 – 188

Question 12.
607 – 492

Question 13.
3,593 + 1,208

Question 14.
6,921 + 451

Question 15.
7,264 – 2,835

Question 16.
1,847 + 3,086

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?

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?

Set F, pages 36–38

Estimate: 400 + 700 = 1,100

Remember to regroup if necessary when adding whole numbers.

Question 1.
215 + 8,823

Question 2.
14,296 + 444

Question 3.
2,417 + 3,573

Question 4.
572 + 941

Question 5.

Question 6.

Question 7.

Question 8.

Set G, pages 40–41

Find 831 – 796.
Estimate: 830 – 800 = 30

Remember you may need to regroup before you subtract.

Question 1.
415 – 323

Question 2.
673 – 294

Question 3.
186 – 77

Question 4.
4,978 – 2,766

Question 5.

Question 6.

Question 7.

Question 8.

Set H, pages 42–43

Find 400 – 378.
Estimate: 400 – 380 = 20
Regroup 4 hundreds to tens and ones.

Question 1.
700 – 255

Question 2.
1,054 – 438

Question 3.
320 – 111

Question 4.
4,508 – 2,613

Question 5.

Question 6.

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?