Adding and subtracting decimals

When adding and subtracting decimals, remember to keep the decimal points in line in the question and the answer.

Adding decimals

Question

David is doing some DIY. He buys a {2}~m length of wood.

He needs to cut two pieces of wood - one of length {0.6}~m and one of length {1.02}~m.

What is the total length of wood that David needs to cut?

Diagram of a saw and three pieces of wood

Add 0.6 and 1.02

Adding decimals diagram: 0.6 + 1.02 = 1.62

So the total length of wood that David needs to cut is {1.62}~m.

curriculum-key-fact
You can add zeros to the end of a decimal without affecting its value, so 0.6 is the same as 0.60.

Subtracting decimals

Question

David originally had {2}~m of wood. What is the length of the piece of wood that is left over?

You can add zeros after a decimal point without affecting its value, so {2} is the same as {2.00}.

David cut off {1.62}~m, so we need to calculate 2 - 1.62

Short division diagram

This means that there is {0.38}~m of wood left over.