Set A, pages 24-26

Add 53 + 11 + 7 using mental math.

53 and 7 are compatible numbers, and the Commutative Property of Addition allows you to add in any order.

53 + 11 + 7 = 53 + 7 + 11
= 60 + 11
= 71

Remember that you can use compatible numbers or compensation to find sums and differences.

Question 1.
67 + 28

Question 2.
130 + 470

Question 3.
35 + 14 + 6

Question 4.
276 – 99

Question 5.
96 + 234 + 4

Set B, pages 28–29

Round 12.087 to the underlined place.
12.087 Look at the digit following the underlined digit. Look at 7.
Round the 8 to the next higher digit because 7 > 5.

Remember that rounding a number means replacing it with another number that tells about how much or how many.

Question 1.
10.245

Question 2.
9.145

Question 3.
67,901

Question 4.
99,102

Set C, pages 30–32
Estimate 19.9 + 17.03

19.9 + 17.03 is about 37.

Remember that you can also use compatible numbers to estimate.

Question 1.
76 + 23

Question 2.
15.01 – 4.4

Question 3.
8,001 + 2,890

Question 4.
25,003 – 12,900

Set D, pages 34–36

Find 6,259 – 2,488.
Estimate: 6,000 – 2,000 = 4,000.
Subtract each place, starting from the right.

The answer 3,771 is reasonable because it is close to the estimate.

Remember to first estimate and then check that your answer is reasonable.

Question 1.

Question 2.

Question 3.

Question 4.

Question 5.
72,555 + 38,055

Set E, pages 38-41

Find 7.83 – 3.147.
Estimate: 8 – 3 = 5.
Step 1
Write the numbers. Line up the decimal points. Annex zeros to show place value.

Step 2
Subtract as you would whole numbers. Bring the decimal point straight down in the answer.

Step 3

The difference is reasonable because 4.683 is close to the estimate of 5.

Remember to line up the decimal points before you add or subtract.

Question 1.
3.77 + 4.66

Question 2.
12.68 + 31.919

Question 3.
6.142 + 1.322

Question 4.
67.8 + 14.755

Question 5.
7.029 + 48.7

Question 6.
10.93 + 0.967

Question 7.
9.21 – 1.72

Question 8.
15.51 – 11.302

Question 9.
5.7 – 0.623

Question 10.
16.209 – 14.5

Question 11.
17.099 – 9.7

Question 12.
81.12 – 37.202

Set F, pages 42-44

Steve exercises 910 minutes a week in the summer. This is 190 minutes more than he exercises each week during the school year. How many minutes a week does he exercise during the school year?
Draw a bar diagram to show the main idea.

Let m = minutes per week of exercise during the school year.

Martin exercises 720 minutes a week during the school year.

Remember that drawing a picture can help you before writing an equation to solve a problem.

Draw a picture and write an equation. Solve.

Question 1.
Jay’s parents celebrated their 25th wedding anniversary in 2005. In what year did they get married?
The two fifth-grade classes at school are having a fundraiser. The first class raised $2,187. Both classes raised$4,136 together. How much did the second class raise?