The discount is not the answer
The Short Answer
Almost every percentage question in the 11+ can be built from ten per cent and one per cent without a calculator. The marks are lost at the end rather than in the middle: a question about a sale usually asks for the price after the discount, not the discount itself, and the discount is always one of the options.
Two building blocks, everything else assembled
You only ever need two.
Ten per cent — divide by ten. One per cent — divide by a hundred.
Everything else is built from those. Five per cent is half of ten. Twenty per cent is double it. Twenty-five per cent is a quarter of the amount. Thirty-five per cent is ten plus ten plus ten plus five.
35% of 80: ten per cent is 8, so that is 8 + 8 + 8 + 4 = 28. No calculator, no percentage button, no multiplying by 0.35 under time pressure.
And four worth simply recognising
50% is a half. 25% is a quarter. 10% is a tenth. 20% is a fifth.
Those four cover a lot of ground and turn the question into a single division. A child who sees 25% of 40 and thinks quarter has answered before a child building up from ten per cent has finished.
The mark that gets lost at the end
Here is where the marks actually go, and it is not in the arithmetic.
Increase and decrease
Find the change, then compare it with what you started with.
A price rising from £40 to £50 is a change of £10. Ten pounds out of the original forty is a quarter — 25%.
The mistake is comparing against the final amount instead. Ten out of fifty is 20%, which is a perfectly good sum and the wrong answer to this question. Percentage change is always measured against the original.
Where do pupils lose marks?
Giving the discount instead of the price, which is the big one.
Measuring a change against the new amount rather than the old.
Reaching for a decimal multiplication under pressure and slipping a place.
Taking the percentage of the wrong number in a two-step question — the second percentage is usually of the new amount, and the question will say so.
Try it yourself
Build each one from ten per cent. Then read the question again before writing the answer.
- What is 30% of 60?
- What is 15% of 240?
- A coat costs £40 and is reduced by 15%. What is the sale price?
- What is 60% of 45?
- A price rises from £40 to £50. What is the percentage increase?
- 18. Ten per cent of 60 is 6, so thirty per cent is three lots of 6.
- 36. Ten per cent of 240 is 24, five per cent is half of that at 12, and 24 + 12 is 36.
- £34. Ten per cent is £4, five per cent is £2, so the discount is £6 — and the sale price is £40 − £6. Answering £6 is the trap, and £6 will be one of the options.
- 27. Ten per cent of 45 is 4.5, and six lots of 4.5 is 27. Halving to 5% first also works: 45 − 10% − 10% − 10% − 10% is slower but just as correct.
- 25%. The rise is £10, and £10 out of the original £40 is a quarter. Percentage change is always measured against what you started with, not what you ended with.
How much practice does this type need at home?
Sale signs. Genuinely — a shop window offering 30% off is a complete question, and the follow-up is always the same: so what does it cost now? That second question is the one the paper asks and the one children skip.
Restaurant bills work too: ten per cent of the total, then a bit more, is exactly the building method under a different name.
Free: a Maths workbook
Questions across the Maths question types, with the method printed at the top and full answers at the back. One workbook for the whole strand, not a sheet per question type.
Frequently Asked Questions
What is the fastest way to find a percentage without a calculator?
Build it from ten per cent. Divide by ten to get 10%, halve that for 5%, divide by a hundred for 1%, and assemble whatever you need. Thirty-five per cent is 10 + 10 + 10 + 5. It sounds longer than multiplying by 0.35 and it is considerably faster in practice, because every step is a division by ten or a halving.
Why does my child get the working right and the answer wrong?
Because the question asked for the price and they gave the discount. It is the single commonest way to lose a mark on this topic, and it is not a maths error at all — the arithmetic was perfect. The fix is mechanical: underline the last sentence of the question before starting, and check the answer against it before writing anything down.
How do you work out a percentage increase or decrease?
Find the change, then compare it with the original amount. A rise from £40 to £50 is a change of £10, and £10 out of £40 is a quarter, so 25%. The mistake to avoid is comparing against the final amount — £10 out of £50 would be 20%, which is a different and wrong answer.
Which percentages should be instantly recognisable?
Fifty per cent as a half, twenty-five as a quarter, ten as a tenth, and twenty as a fifth. Those four cover a large share of the questions and turn them into single divisions. A child who sees 25% of 40 and thinks 'a quarter' answers before a child who starts building from ten per cent has finished.
Sources
- GL Assessment — 11+ familiarisation materials and question type descriptions Published 2025.
- Clever Clogs Academy — our own Year 4 and Year 5 lesson records, Winslow Published September 2025 to July 2026.
We are not affiliated with, endorsed by or connected to GL Assessment or Buckinghamshire Council. Test arrangements change; always check the council's own pages for the current year's dates.
We Teach This Method Every Week in Winslow
Groups of no more than six pupils with two qualified teachers, in person or online. Come and see a session before you decide.