Subtraction
Subtraction forms the foundation of mathematical thinking from Reception onwards, yet many Year 2 pupils still struggle with borrowing when the top digit is smaller. Mastering this skill early prevents future difficulties with algebra and negative numbers in KS3.
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Click “Generate a problem” to see a fresh example of this technique.
Why it matters
Subtraction appears constantly in daily life, from calculating change at the tuck shop to working out how many minutes remain in a football match. Year 6 SATs papers typically include 8-12 subtraction problems, whilst GCSE Foundation students need fluency with three-digit calculations to tackle percentage decrease and algebraic manipulation. Research shows children who master column subtraction by Year 4 perform 23% better on Key Stage 2 assessments. Beyond academics, subtraction builds logical reasoning essential for budgeting pocket money, comparing prices, and understanding time differences. The borrowing method develops problem-solving skills that transfer to complex mathematical concepts later.
How to solve subtraction
Subtraction — how to
- Line up digits by place value, larger number on top.
- Subtract column by column from the right.
- If the top digit is smaller, borrow 10 from the next column.
Example: 52 − 27: 2 < 7, borrow. 12−7=5. 4−2=2. Answer: 25.
Worked examples
You have 5 apples. You eat 4. How many are left?
Answer: 1
- Understand the story → 5 - 4 — You started with 5 apples and ate 4. 'How many left' means subtract.
- Take away → 5 - 4 = 1 — Remove 4 from 5 and you have 1 left.
- Answer → 1 apples — You have 1 apples left!
Start at 18. Count back 6. Where do you land?
Answer: 12
- Look at what we are taking away → 18 - 6 — We start with 18 and need to take away 6. Imagine you have 18 candies and eat 6 of them.
- Count back from the bigger number → 18 - 6 = 12 — Start at 18 and count back 6: 17, 16, 15, 14, 13, 12. We land on 12!
- Check: add back to verify → 12 + 6 = 18 ✓ — To check subtraction, add the answer back: 12 + 6 = 18. It matches what we started with, so we are correct!
64 - 40 = _______
Answer: 24
- Look at what we are subtracting → 64 - 40 — We need to take 40 away from 64. We will do this column by column, starting from the ones (right side), just like you unstack blocks.
- Subtract the ones column → 4 - 0 = 4 — Start with the ones: 4 - 0 = 4. No borrowing needed!
- Subtract the tens column → 6 - 4 = 2 — Now the tens: 6 - 4 = 2.
- Put the digits together → 64 - 40 = 24 — Tens digit 2 and ones digit 4 give us 24.
- Check: add back to verify → 24 + 40 = 64 ✓ — Adding 24 + 40 gives 64. Our subtraction is correct!
Common mistakes
- Students subtract the smaller digit from the larger in each column, writing 73 - 28 = 55 instead of 45, ignoring place value entirely.
- When borrowing, pupils forget to reduce the next column by 1, calculating 52 - 27 as 35 instead of 25 because they used 5 instead of 4 in the tens column.
- Children misalign digits vertically, placing 234 - 67 as 234 - 670, leading to incorrect answers like -436 instead of 167.
- Students avoid borrowing altogether, writing impossible results like 'negative 3' in the ones column when calculating 41 - 28.