Mental Math
Estimation
Addition
Subtraction
Problem Solving
100

8.6 +23.4 + 1.4

33.4

100

Round to nearest ten to estimate.

358 + 293

650

100

Find the sum

7.06 + 0.85

7.91

100

Find the Difference

24.07-5.31

18.76

100

Lucy bought 2.12 pounds of pears and 4.35 pounds of apples. Fid how many more pounds of apples than pears Lucy bought.

2.23 pounds

200

15.3 + 1.1 +1.7

18.1

200

Round to nearest whole number to estimate the difference 

15.01 - 4.4


11

200

Find the sum

53.2 + 29.4

82.6

200

Find the Difference

51.92 - 28.03

23.89

200

Kayla's dollhouse has 15.15 square feet downstairs and 6.45 square feet upstairs. What is the estimated total area if you round the decimals to the nearest tenth?

21.7 square feet

300

27 - 9.9

17.1

300

Round to the nearest tenth to estimate the sum

80.01 + 2.89

82.9

300

Find the sum

0.02 + 12 + 0.88

12.9

300

Find the Difference

23.6 - 8.87

14.73

300

Ed is training for a race. He ran 12.56 miles on one day, 12.98 miles the second, and 13.04 miles the third day.

A. What is his combined distance for the first three days?

B. How much farther did he run the second day than the first?

A. 38.58 miles total

B. 0.42 miles farther

400

13.5 + 5.7 + 36.5

55.7

400

Round to the nearest thousand to find the difference

25,003 - 12,900

12,000

400

Find the sum

16.8 + 17 + 3.94 + 101.68

139.42

400

Find the Difference

127.3 - 16.65

110.65

400

Amber bought a hardcover book for $23.70 and a paperback for $6.91.

A. How much did she spend in all?

B. If she paid with 2 twenty-dollar bills, how much change did she get?

A. $30.61 spent

B. $9.39 change

500

205.4 - 99.7

105.7

500

Use compatible numbers to estimate the difference

22.4 - 16.2

5  or  6

500

Find the Sum

10,892.03 + 89.2 + 345,678.99

356,660.22

500

(35.8 + 358) - 234.92

158.88

500

Daria bought a skein of alpaca yarn for $47.50, a skein of angora yarn for $32.54, a skein of wool yarn for $16.87 and a pair of knitting needles for $3.86. She pays with a 100 dollar bill and a 20 dollar bill.

A.  How much did she spend in all?

B. How much change did she receive?


A. $100.77 total cost

B. $19.23 change