✏️ Decimal Column Addition and Subtraction

About Decimal Column Addition and Subtraction

Almost every mistake in decimal addition is an alignment mistake. A pupil who lines up the last digit instead of the decimal point will add tenths to hundredths and produce an answer that is wrong by a factor of ten while every individual digit sum is correct — which is why it goes unnoticed. This worksheet mixes decimals of different lengths from the middle levels onwards specifically so that lining up the right-hand edge stops working, and the decimal point has to be found. The arithmetic behind every question is done in whole numbers scaled by a power of ten and only converted to a decimal when it is printed, so no answer on these sheets can carry a floating-point artefact — the sort of trailing nonsense that turns a clean sum into an unmarkable one. Subtraction questions are constructed to stay positive, since negative answers belong on the integers worksheet rather than here. Decimal places, number size and the mix of addition and subtraction all widen across the five levels. Twelve questions per page in two columns with room to set the working out. Each level prints as a clean A4 sheet in black and white and downloads with its own separate answer key.

Common questions

Why are the decimals different lengths?

So that lining up the right-hand edge stops working and the decimal point has to be found. That is the mistake this worksheet targets.

Can an answer be negative?

No. Subtraction questions are built to stay positive; negative answers belong on the integers worksheet.

Are the answers exact?

Yes. The arithmetic is done in whole numbers scaled by a power of ten, so no floating-point artefact can reach the page.

Is an answer key included?

Yes. Every level downloads with its own separate answer key PDF.