# Line Up the Points

Adding decimals is easy. When we worked with whole numbers, we lined up the ones column before we started to add. You can still do that with decimals, but sometimes you won't have a value in the ones column. What do you do? Line up the decimal points! The rest is plain old addition where you start on the right and move to the left. If you have any missing spaces, just think of them as zero values or write the zeros on your own.

Example:
 0.253 + 0.3     ???

We lined up the decimal points for you but there are some spaces. Let's fill them in with zero values.
 0.253 + 0.300 ???

When you work with decimals and the metric system, it's polite to write that first zero in the answer so the reader knows the value is less than one. It's just easier to read than starting the number with a dot.

Let's try an example with values greater than one...

Example:
Add the values 352.1587 and 402.008. (352.1587 + 402.008 = ?)

Steps to Solve:
• Line up the decimal points.
 352.1587 + 402.008   ?

 352.1587 + 402.0080 ?

• Start adding from the right column (ten-thousandths)
 352.1587 + 402.0080 754.1667

That example had a mix of regrouping and decimal addition. Take your time and start from the right after you lined up the points. Don't get tricked by numbers like these...

Example:
Add the values 149357.5 and 1.493575 (149357.5 + 1.493575 = ?)

Steps to Solve:
• Line up the decimal points and you'll see how easy this is.
 149357.5           +         1.493575 ?

• Toss in some zeros if it is easier to see.
 149357.500000 +         1.493575 ?

## Related Activities

 Adding Tenths on a Number Line - Play Activity Identify Thousandth Values - Play Activity

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