Adding decimals is similar to adding whole numbers.

I strongly recommend though that you review or study the lesson about adding whole numbers before starting this lesson.

Let us start our lesson with something simple.

Look at the following additions:

This will ensure that you do not add tenths to hundredths or hundredths to thousandths and so forth...

In the first addition problem, we are adding 0.5 to 0.4. It is done in 3 steps!

First, add the tenths (5 and 4) to get 9 tenths

Then, add the ones ( 0 and 0) to get zero.

Finally, write the decimal. It is place immediately after the ones place

Now try to add the followings:

Recall that 1 tenth = 0.1, so 10 tenths = 10 × 0.1 = 1

Therefore, To add these decimals, we must carry over a 1 to the ones place.

The following demonstrates how to add the first two problems:

You could have gotten the answers by adding horizontally.

0.6 + 0.7 = 0.6 + 0.4 + 0.3 = 1 + 0.3 = 1.3 (0.7 = 0.4 + 0.3)

0.8 + 0.8 = 0.8 + 0.2 + 0.6 = 1 + 0.6 = 1.6 (0.8 = 0.2 + 0.6)

0.9 + 0.7 = 0.9 + 0.1 + 0.6 = 1 + 0.6 = 1.6 (0.7 = 0.1 + 0.6)

In practice, when adding vertically,there is no need to write down all those tenths. You can pretend that the decimal point does not exist and try adding decimals as if you were adding whole numbers.

Here is how if we are adding 0.6 to 0.7 and 0.8 to 0.8

Other examples: