Number System: Adding and Subtracting Decimals

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.

Posted in: Adding and Subtracting Decimals, Number System