Percentages Test
mediumFinding a percentage in your head is one of the most useful maths skills, from discounts to exam questions. This test asks ten questions per round: Easy uses 10%, 20%, 25% and 50%; Medium adds 5%, 15%, 30% and others; Hard brings in 12.5%, 37.5% and 65%.
5%, 15%, 30%, 40%, 60%, 75%, 80% and 90% of round numbers.
Every answer is a whole number. The chart shows the common percentages worked out for 240, and the shortcuts below show how to build any percentage from 10%, 5% and 1%.
Quick-reference percentages (of 240)
| Percentage | Fraction | Shortcut | Of 240 |
|---|---|---|---|
| 1% | 1/100 | Divide by 100 | 2.4 |
| 5% | 1/20 | Half of 10% | 12 |
| 10% | 1/10 | Move the decimal one place | 24 |
| 12.5% | 1/8 | Halve three times | 30 |
| 20% | 1/5 | Divide by 5 | 48 |
| 25% | 1/4 | Halve twice | 60 |
| 33⅓% | 1/3 | Divide by 3 | 80 |
| 50% | 1/2 | Halve it | 120 |
| 75% | 3/4 | Three quarters | 180 |
Mental shortcuts for percentages
- 10%: move the decimal point one place to the left. 10% of 460 = 46.
- 5% is half of 10%, and 1% is a tenth of 10%. Build other percentages from these pieces.
- 15% = 10% + 5%. For 15% of 80: 10% is 8, 5% is 4, so the answer is 12.
- 35% = 3 × 10% + 5%. For 35% of 60: 10% is 6, three lots is 18, 5% is 3, so the answer is 21.
- Swap the numbers: x% of y equals y% of x. 8% of 25 is the same as 25% of 8, which is 2.
- 12.5% is one eighth, so halve three times: 12.5% of 64 is 32, 16, then 8.
Frequently asked questions
How do you find 10% of a number?
10%: move the decimal point one place to the left. 10% of 460 = 46.
How do you work out 15% of a number in your head?
15% = 10% + 5%. For 15% of 80: 10% is 8, 5% is 4, so the answer is 12.
What is 12.5% of 80?
12.5% is one eighth, so 12.5% of 80 = 80 ÷ 8 = 10.
What is 35% of 60?
35% = 3 × 10% + 5%. 35% of 60: 10% is 6, three lots is 18, 5% is 3, so the answer is 21.
What is the fastest way to calculate percentages?
Swap the numbers: x% of y equals y% of x. 8% of 25 is the same as 25% of 8, which is 2.
How is the speed maths test scored?
Each test has 10 questions. Answer 8 or more correctly to pass. Your time is recorded for the whole test, and your best time for each test and level is saved on your own device, so you can try to beat it.