Adding and Subtracting Decimals

Estimate Sums

100

ESTIMATE by rounding:   22 + 13

20 + 10 = 30

200

ESTIMATE by rounding:   15.01 + 4.4

15 - 4 = 19     OR     15 + 5 = 20

300

ESTIMATE by rounding: 80.1 + 2.89

80 + 3 = 83

400

ESTIMATE by rounding:   9.5 + 8.6

10 + 9 = 19

500

ESTIMATE by rounding:    3.41 + 34.7

3 + 35 = 38     OR    3 + 30 = 33

Estimate Differences

100

ESTIMATE by rounding:    24 - 11

20 - 10 = 10

200

ESTIMATE by rounding:    9.2 - 3.1

9 - 3 = 6    OR    10 - 3 = 7

300

ESTIMATE by rounding:    42.53 - 12.5

40 - 10 = 30    OR     43 - 13 = 30

400

ESTIMATE by rounding:    39.41 - 15.6

40 - 20 = 20    OR    40 - 15 = 25

500

ESTIMATE by rounding:    28.4 - 19.5

30 - 20 = 10     OR 28 - 20 - 8

Add Decimals

100

0.02 + 0.89

0.91

200

0.34 + 0.34

0.68

300

3.49 + 2.1

5.59

400

23.3 + 5.09

28.39

500

307.07 + 84

391.07

Subtract Decimals

100

5.6 - 2.5

3.1

200

42.83 - 2.1

40.73

300

5.7 - 0.62

5.08

400

19 - 7.5 

11.5

500

12 - 3.72

8.28

Word Problems

100

Ron jogged 2.2 km, Mike jogged 3.7 km. How far did Ron and Mike jog altogether?

5.9 km

200

Kathi had a rope of 63.45 m. She cut the rope into two pieces. If the length of one piece was 23.59 m, what was the length of the other piece?

39.86 m

300

Julia and Mary go to the movies. Julia buys a popcorn and soda for $8.40 and Mary buys Skittles and a water for $5.75. How much did Julia and Mary spend?

$14.15

400

Chris feeds the dog 2.4 cups of dog food from a new bag of dog food. If the new bag of dog food holds 20 cups, how much is left in the bag after he feeds her TWICE?

15.2 cups are left

2.4 + 2.4 = 4.8   (total fed Chris fed her TWICE means 2 times)

20 - 4.8 = 15.2

500

Lucy took a math test and got 13.5 points take off. If the test was out of 50 points, how many points did Lucy get correct?

36.5 points correct