Mental Computation and Estimation

Round to 10

100

Round to the nearest ten. 

42

40

200

Round to the nearest 10. 

68

70

300

Round to the nearest 10. 

96

100

400

Round to the nearest 10. 

182

180

500

Round to the nearest 10. 

298

300

Round to 100

100

Round to the nearest 100. 

218

200

200

Round to the nearest 100. 

842

800

300

Round to the nearest 100. 

983

1,000

400

Round to the nearest 100. 

5,302

5,300

500

Round to the nearest 100. 

6,377

6,400

Identify the operation

100

Which operation should be used to solve: 

Anna walked 2 miles in the morning and 3 miles in the afternoon. How far did she walk in all?

addition

200

Which operation should be used to solve:

Sarah's class has 20 students. Twelve are boys. How many are girls?

subtraction

300

Which operation should be used to solve: 

Ashley needs to save $175 for a new phone. So far, she has $48 saved. How much more does she need to save?

subtraction

400

Which operation would be used to solve: 

Frank baked 120 cookies. Each box will hold 10 cookies. How many boxes does he need?

division

500

Which operation would be used to solve: 

Beth raked 4 lawns. Each lawn took 40 minutes to rake. How many minutes did she rake altogether?

multiplication

Estimate Sums and Differences

100

Estimate the sum: 

48 + 24 = 

50 + 20 = 70

200

Estimate the difference: 

793 - 231 =

800 - 200 = 600

300

Estimate the sum:

121 + 583 = 

100 + 600 = 700

400

Estimate the difference. Explain how you estimated it. 

49 + 23 + 18 =

Round 49 to 50. Round 23 to 20. Round 18 to 20. 

Add 50 + 20 + 20 = 90

500

Estimate the answer. Explain how you estimated. 

534 - 287 +123 =

Round 534 to 500. Round 287 to 300. Round 123 to 100. 

First, subtract 500 - 300 = 200

Then, add 200 + 100 = 300. 

Estimation Word Problems

100

Patrick ordered 132 cookies and 188 cupcakes. About how many desserts did Patrick order?

A) 200

B) 300

C) 400

D) 500

B) 300

200

This morning Jamie had 94 crafts to finish. So far, he has finished 38 crafts. About how many crafts does he have left to do?

50 crafts

90 - 40 = 50

300

Three puppies went to the vet. The first puppy weighed 28 ounces. The second puppy weighed 31 ounces. The third puppy weighed 43 ounces. What is the best estimate for their combined weight?

30 + 30 + 40 = 100 ounces

400

Phillip walked for 47 minutes on Monday, 68 minutes on Tuesday, and 42 minutes on Wednesday. If his goal is to walk 200 minutes each week, about how many minutes does he still need to walk?

50 + 70 + 40 = 160

200-160 = 40 minutes

500

Jeff started with $162 in his bank account. Then, he spent $47. After that, he added $61 to his bank account. What equation would best estimate his new balance? 

A) 160 + 50 + 60 = 

B) 160 - 50 - 60 =

C) 160 - 40 + 60 = 

D) 160 - 50 + 60 = 

D) 160 - 50 + 60 =