Adding and subtracting decimals

​​In a nutshell

Adding and subtracting decimals follows exactly the same procedure as adding and subtracting whole numbers. However, decimals require a better understanding of place value.

The column method with decimals

Adding and subtracting using the column method also works for decimals. However, there are a few things to take note of.

Reminder when using the column method with decimals

• Remember to line up all the numbers that come after the decimal point as well - so the tenths, hundredths, thousandths and so on.
• Use zero as a placeholder if one number has fewer place values than the other.
• It is possible to "carry over a one" or "borrow a one" from the units digit to the tenths digit - the decimal point isn't a barrier!
• The decimal point should be aligned under the answer line also.
  

Example: subtraction

What is $$2.198-0.52$$?

Align the two numbers as normal, making sure to line up the decimal point and all digits after the point.

Note how $$0.52$$ has no thousandths digit, but $$2.198$$ does. So, add zero as a placeholder so both numbers have the same amount of digits. $$0.52$$ is hence written as $$0.520$$.

​$$\underline{2.198-0.52=1.678}$$​​

Example: addition

What is $$12.34+9.75$$?

​$$\underline{12.34+9.75=22.09}$$​​