Adding and Subtracting Decimals

Adding decimals is easy if you keep your work neat

To add decimals, follow these steps:

  • Write down the numbers, one under the other, with the decimal points lined up
  • Put in zeros so the numbers have the same length
  • Then add using column addition, remembering to put the decimal point in the answer

Example: Add 1.452 to 1.3

Line the decimals up:     1.452
    + 1.3
       
"Pad" with zeros:     1.452
    + 1.300
       
Add:     1.452
    + 1.300
      2.752

Example: Add 3.25, 0.075 and 5

Line the decimals up:     3.25
      0.075
    + 5.
       
"Pad" with zeros:     3.250
      0.075
    + 5.000
       
Add:     3.250
      0.075
    + 5.000
      8.325

That's all there is to it - just remember to line up the decimals, then add normally.

Subtracting

To subtract, follow the same method: line up the decimals, then subtract.

Example: What is 7.368 − 1.15 ?

Line the decimals up:     7.368
    1.15
       
"Pad" with zeros:     7.368
    1.150
       
Subtract:     7.368
    1.150
      6.218

To check we can add the answer to the number subtracted:

Example (continued): Check by adding 6.218 to 1.15

Line the decimals up:     6.218
    + 1.15
       
"Pad" with zeros:     6.218
    + 1.150
       
Add:     6.218
    + 1.150
      7.368

It matches the number we started with, so it checks out.