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Decimal Rule
Addition of Decimals
Subtraction of Decimals
Multiplication of Decimals
Division of Decimals
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
.6 x 2.1 =
1.26
100
.25 divided by .05 =
5
200
How do you subtract decimals?
You line up the decimals and then subtract the numbers.
200
.004 + 5.1 =
5.104
200
95.29 - 1.3 =
93.99
200
4.25 x 21 =
89.25
200
3.87 divided by .9 =
4.3
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
.9843 + 2.67 =
3.6543
300
125 - .68 =
124.32
300
.03 x .03 =
.0009
300
.425 divided by .005 =
85
400

How do you multiply decimals?

You multiply the numbers as whole numbers ignoring the decimal points.  

Place the decimal in at the end by counting 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 + .030 =
7.81
400
.468 - .059 =
.409
400
2.003 x .05 =
.10015
400
.848 divided by 8 =
.106
500

How do you know where to place the decimal point in a decimal multiplication problem?

You count the number of place values you shifted the decimal point to the right.

Then, shift the decimal point back to the left that same number of place values.

500
8.07 + .0976 + 23.3 + 48 =
79.4676
500
5.45 - 3.799 =
1.651
500
.312 x 1.67 =
.52104
500
.4564 divided by .04
11.41