Finding 50%, 25% and 10% Mentally

P3Finding 50%, 25% and 10%

The three percentages you can always find in your head.

50%, 25% and 10% have shortcut routes — halve, halve again, divide by ten.

Find them mentally.

50%
halve it
50% of 80 = 40

25%
halve twice
25% of 80 = 20

10%
÷ 10
10% of 80 = 8

These three unlock almost every other percentage: 5% is half of 10%; 30% is 3 × 10%.

Learn the 3 Shortcuts

150% → halve.

Half of the amount. 50% of 64 = 32.

64 ÷ 2 = 32

225% → halve, halve again.

A quarter. 25% of 64: half is 32, half again is 16.

64 → 32 → 16

310% → divide by 10.

Digits slide one place right. 10% of 64 = 6.4.

64 ÷ 10 = 6.4

💡 Key Idea10% is the master key: once you have 10%, you can build 20%, 30%, 5%, 15% — almost anything.

Worked Example

Find 50%, 25% and 10% of £120.

50%

120 ÷ 2 = 60

£60

25%

60 ÷ 2 = 30

£30

10%

120 ÷ 10 = 12

£12

✓ Sense-check: 25% (£30) is half of 50% (£60) ✓

Watch Out! Common Mistakes

Dividing by the percentage.

10% of 64 = 64 ÷ 10 = 6.4 ✓ but 25% of 64 = 64 ÷ 25 ✕

Careful! ÷10 works for 10% only because 10% = 1/10. For 25%, divide by 4 (25% = 1/4).

Halving once for 25%.

25% of 80 = 40 ✕

Wrong! 40 is 50%. Halve twice: 80 → 40 → 20.

Sliding the wrong way for 10%.

10% of 64 = 640 ✕

Wrong! 10% is smaller than the amount: 64 ÷ 10 = 6.4.

⬇ Cheat Sheet

FINDING 50%, 25% AND 10%

50% → halve.
25% → halve, then halve again.
10% → divide by 10.
Build others from 10%: 5% = half of 10%; 30% = 3 × 10%.

Example: of £120 → 50% = £60 · 25% = £30 · 10% = £12

📖 Continue Your Journey

✓ P1 What Are Percentages?✓ P2 Percentages, Fractions and Decimals P3 Finding 50%, 25% and 10%P4 Percentage of an Amount P5 Percentage Increase P6 Percentage Decrease P7 Percentages and Money P8 One Number as a Percentage of Another P9 Comparing with Percentages P10 Percentage Change P11 Reverse Percentages P12 Percentage Problem Solving

→

Next Lesson: P4 Percentage of an AmountBuild any percentage from 10% and 1%.

📄 Free printable: Download the Finding 50%, 25% and 10% cheat sheet (PDF) — keep it by your child's desk.

Quick summary

50% of an amount: halve it.
25%: halve, then halve again.
10%: divide by 10 — digits slide one place right.
These three are the building blocks for every other percentage.

Frequently asked questions

What is the quickest way to find 10% of a number?

Divide by 10 — move every digit one place right. 10% of 64 is 6.4; 10% of £120 is £12.

How do you find 25% of an amount mentally?

Halve it twice. 25% of 80: half is 40, half again is 20.

Why learn mental percentage shortcuts?

They're faster than written methods, they work in shops and restaurants, and 11+ papers reward children who can chain them: 35% = 25% + 10%.

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