Adding and Subtracting Decimals

The rules for adding and subtracting decimals are similar to the general rules for adding and subtracting integers. The most important point is to align the decimal points correctly. For example, consider adding the following decimal numbers. 3.4 + 12.802 There are three steps to finding this sum.

1

Line up the Decimal Points

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The first step is to line up the decimal points. The sum is written so that the decimal points are on top of each other.

The numbers are now written vertically. A place value chart can also be used to align the decimal places.

2

Place Zeros at the End of a Decimal If Needed

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The first number does not have the same number of decimal places as the second number. Place zeros so that the numbers have the same number of decimal places.

Now that the decimal digits in each of the numbers are equal, it will be easier to add or subtract these numbers.

3

Add Digits with the Same Place Value

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Temporarily ignore the decimal point and add the digits that have the same place value. This is the same as adding two integers. After that, bring down the decimal point.

The sum of the given numbers is 16.202.

Note that the subtraction of decimals is done in the same way.