When adding or subtracting decimals, the first thing to do is lining up those decimals. We’ve got 4.23 and 9.075. The same applies to subtractions. 5.629 – 0.45.

If we have empty spaces, we can fill these in with just zeroes.

Adding decimals really is easy. When we’re working with whole numbers, just first line up the 1s (ones) column before starting to add. We can do the same with decimals, though sometimes we won’t find any value in the 1s (ones) column.

Then what do we do? We are Lining up our decimal points! For the rest, it is simply an old-fashioned addition where we begin on the right side and then move to the left side. When we see some missing spaces, think of those just as zero (0) values, or you can write those zeros here on your own.

For example:

0.253 plus+ 0.3 equals ?

When we line up the decimal points, you’ll see a few spaces. So let’s fill them up with zeros.
0.253
0.300

After adding our columns, the sum is simply 0.553.

When working with decimals in the metric system, it is custom to write that first zero (0) in your answer, so readers know that the value is less than 1 (one). This simply easier reading than when you would start that number with a period or dot.

Subtracting Decimals

Well, subtracting decimals isn’t hard either. While working with whole numbers earlier, we had to line up the 1’s (ones) column before starting our subtraction process. Well, we can still do the same with decimals, yet at times, we won’t see a value in the 1’s (ones) column.

So what do we do? We just line up our decimal points here as well! All the rest is simple old-fashioned subtraction, where we begin at the right side, after which we move on to the left side. If you see any missing or empty spaces, consider them as zero (0) values, or you can fill in the zeros by yourself.

For example:

0.253 – 0.03 equals ?

When we line up our decimal points, you’ll see a few empty spaces. We’ll fill these in with zero (0) values.

0.253
0.030

When working with decimals or the metric system, it is common to write the first zero (0) in your answer, so readers know the values are less than 1 (one). This simply easier reading than when we would begin that number with a period or a dot.

For example:

0.101 – 0.0235 equals ? First, we’ll need to borrow for this problem. We’ve done that before. This looks like we need a zero (0) at the end of our minuend: 0.1010 – 0.0235. So you see. Our answer is simply 0.0775.

### Video Summary and Quiz

1. Simplify the given expression.

$$-2 - 0.49$$
A.
B.
C.
D.

Question 1 of 2

2. Simplify.

$$16.4 + (-41.205)$$
A.
B.
C.
D.

Question 2 of 2

Next lesson: Multiplying Decimals

Last Updated on April 12, 2021.