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How Does Adding and Subtracting Decimals Work?

adding and subtracting decimals: girl reading a book on her belly

Adding and subtracting decimals is actually very similar to the addition and subtraction of whole numbers, which don’t have decimals. However, seeing all those numbers to the right of the decimal point can be intimidating and makes a problem seem much harder than it actually is.

In this guide, we'll show you just how simple it is to add and subtract decimals.

Adding Decimal Numbers

Let's do a quick review of decimal place values. Each place value, or number of decimal places to the right of the decimal point, has a different name:

different decimal place values

When you are given a decimal addition problem, check to see if the two numbers you are given have the same number of digits after the decimal point:

adding and subtracting decimals: decimal addition problem

As you can see, 6.55 has a hundredth place value but 7.089 has a thousandths place value. Because of this, you have to add an extra zero to 6.55 in order to line up the two numbers and add them:

numbers with a thousandth decimal place

Now you can add the two decimal numbers:

adding and subtracting decimals: decimal addition formula

Subtracting Decimal Numbers

Let's subtract the following decimal numbers:

decimal subtraction problem

These numbers do not have the same number of digits to the right of the decimal point. 5.2 has a tenth place decimal, so we have to add two zeros in order to line the two decimal numbers up:

adding and subtracting decimals: subtracting by adding the thousandth decimal place

Now that the zeros have been added, let's proceed with the subtraction of decimals:

subtraction of decimals formula

Adding and Subtracting Decimals — It's Easy!

Now that you've worked through adding and subtracting decimals, you can see just how easy it is. All you have to do is compare the two numbers you are given, add zeros so that they have the same amount of numbers after the decimal point, and proceed with subtraction or addition.

Learning how to add and subtract decimals will make it easier to move on to more complex concepts like dividing and multiplying decimals.

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