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11+ Maths Guide · Year 5–6 · Free lesson

Reverse Percentages

The sale price is £45 after 25% off — so what was it before? Reverse percentages are the classic 11+ stretch question, and the unitary method (find one block, scale to 100%) cracks every one of them.

P11Reverse Percentages
Work backwards to find the original price.
Reverse percentages: you know the sale price — what was it before? (11+ stretch)
A jacket costs £45 after a 25% discount. What was the original price?
£45 is 75% of the original
75% = £45 → 25% = £15
100% = 4 × £15 = £60
Find what 1% (or 25%) is worth, then scale up to 100%.
1

Learn the 3-Step Method

1Work out what % the price represents.

After 25% off, you pay 100 − 25 = 75% of the original.

£45 = 75%

2Find an easy block.

75% = £45, so 25% = 45 ÷ 3 = £15.

25% = £15

3Scale up to 100%.

100% = 4 × £15 = £60.

£60
💡 Key IdeaNever take the percentage of the sale price — the discount was a percentage of the original, which is what you're hunting for.
2

Worked Example

After a 10% price rise, a ticket costs £22. What did it cost before?

What % is £22?
After +10%, the new price is
110% = £22
Find 10%
22 ÷ 11 = 2
10% = £2
✓ 100%
10 × £2 = £20
£20
✓ Check forwards: £20 + 10% (£2) = £22 ✓
3

Watch Out! Common Mistakes

Taking the % off the sale price.
£45 + 25% of £45 = £56.25 ✕

Wrong! The 25% was of the original, not of £45. Working back properly gives £60.

Calling the sale price 100%.
£45 = 100% ✕

Wrong! After 25% off, £45 is 75% of the original.

Not checking forwards.

Always check! Run your answer forwards: £60 − 25% = £45 ✓. If it doesn’t reproduce the question, start again.

Cheat Sheet

REVERSE PERCENTAGES
  1. Decide what % the given price represents (100 − discount, or 100 + rise).
  2. Divide to find an easy block (1%, 10% or 25%).
  3. Scale up to 100% — that's the original.
  4. Check by running the problem forwards.
Example: £45 after 25% off → 75%=£45 → 25%=£15 → original £60.
📄 Free printable: Download the Reverse Percentages cheat sheet (PDF) — keep it by your child's desk.

Quick summary

Frequently asked questions

What is a reverse percentage question?

One where you know the amount after a percentage change and must find the original — like a sale price of £45 after 25% off (original: £60).

Why can't you just add the percentage back on?

Because the discount was a percentage of the original, not of the sale price. Adding 25% of £45 gives £56.25 — the wrong answer.

Are reverse percentages on the KS2 curriculum?

They're beyond the standard Year 6 objectives but appear in grammar-school 11+ papers, so we include them as a clearly-marked stretch lesson.

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