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Decimal Rule
Addition of Decimals
Subtraction of Decimals
Multiplication of Decimals
Powers of Ten
100
How do you add decimals?
You line up the decimals and then add the numbers.
100

58.9 + 3.04 =

61.94

100

3.95 - 2.7 =

1.25

100

0.6 x 2.1 =

1.26

100

0.9 x 10

9

200
How do you subtract decimals?
You line up the decimals and then subtract the numbers.
200

0.004 + 5.1 =

5.104

200
95.29 - 1.3 =
93.99
200

4.25 x 21 =

89.25

200

1.3 x 100

130

300
What do you do if there are not enough digits in the top number to subtract a problem?
You have to add on zero's.
300

0.9843 + 2.67 =

3.6543

300

125 - 0.68 =

124.32

300

0.03 x 0.03 =

0.0009

300

24.98 x 10

249.8

400
How do you multiply decimals?
You multiply the numbers and then you count how many spaces there are to the right of the decimals and count them over to the left in the answer.
400

5 + 2.78 + 0.030 =

7.81

400

0.468 - 0.059 =

0.409

400

2.003 x 0.05 =

0.10015

400

12.9 x 102

1,290

500

What is the most important step to do when adding or subtracting decimals?

Lining up the decimals.

500

8.07 + 0.0976 + 23.3 + 48 =

79.4676

500

5.45 - 3.799 =

1.651

500

0.312 x 1.67 =

0.52104

500

28.95 x 103

28,950