Adding and Subtracting Decimals
To Add or Subtract Decimals:
1)
2)
3)
4)
Align the decimal points in each number.
Fill in any empty decimal places with zeros.
Add or subtract the decimal numbers as if you were adding or subtracting whole numbers.
Place a decimal point in the final answer. Make sure it is aligned with all the other decimal
points.
Hint: Remember that whole numbers such as 12 can be turned into a decimal number by placing a decimal
point to the right of the number.
For example: 12  12.0
Examples:
Add the decimal numbers 125.4, 52.325, and 0.64.
Subtract the decimal numbers 142 and 39.512
125.400
52.325
+ 0.640
178.365
142.000
- 39.512
102.488
Multiplying Decimals
To Multiply Decimals:
Remember, you do not have to line up decimal points when multiplying.
1) Count the number of decimal places in each factor.
6. 8 7
2 decimal places
x 1. 3
+1 decimal place
2) Calculate the sum of all the decimal places. This is the
number of decimal places that will be in your final answer
(product).
3) Multiply the decimals just as you would multiply whole
numbers (Ignore the decimal points while multiplying).
4) Place a decimal point in your answer.
Your final answer should have the same number
of decimal places as the sum of the decimal places
of your factors.
= 3 decimal places
6. 8 7
x 1.3
2061
687X
8.9 3 1
A2
Dividing Decimals
Information you need to know before dividing decimals.
A) Vocabulary:
1) Divisor- the number that an amount is being divided by.
(The divisor does the dividing.)
2) Dividend- the number being divided.
3) Quotient- the answer to a division problem.
B). Division Problems can be written two ways.
8
3 24
Divisor
OR
24  3 = 8
Quotient
Dividend
Divisor
Quotient
Dividend
To Divide Decimal Numbers:
DIVIDE
0 . 4 0.3 6
1) If there is a decimal point in the divisor,
move the decimal point in the divisor to the
0.4
.
0.3 6
RIGHT until it becomes a whole number.
2) If you moved the decimal point in the divisor,
4.
0. 3 .6
move the decimal point in the dividend to the
RIGHT the same number of decimal places.
.
3) Place a decimal point in the quotient space
directly above the new decimal point in the
Decimal point
4. 0 3 . 6
dividend.
4) Divide as if you are dividing whole numbers.
(Ignore the decimal points while dividing.)
0 .9
4. 3.6
-3 6
0
Final Answer = 0.9
Things to keep in mind when moving your decimal points
 Unlike the divisor, it is perfectly acceptable for the dividend to still be a
decimal number after you have moved the decimal point.
 In the dividend, if you need to make more decimal point movements than
there are decimal places, you will need to fill in a zero for each extra decimal
point movement.
A3