Maths, coding, AI & parents
Mental maths tricks and times tables tricks that actually work
Quick mental maths tricks for kids and parents: the 9s finger trick, multiplying by 11, squaring numbers ending in 5, divisibility rules, quick percentages and tips for hard times tables. Every trick explained with an example.
Mental maths gets faster when you know a few good tricks and practise them. Here are shortcuts that really work, each with an example. Try them with the free mental maths practice and the times tables trainer.
Times tables tricks
- The 2s, 4s and 8s are doubling. For 8 × 3, double 3 to get 6, double again to get 12, and again to get 24.
- The 5s: multiply by 10 and halve. 5 × 8 = half of 80 = 40. Answers always end in 5 or 0.
- The 9s finger trick: hold up ten fingers. To do 9 × 7, fold down the 7th finger. The fingers to its left (6) are the tens, and those to its right (3) are the units: 63. Also, the digits of every answer in the 9 times table add up to 9.
- The 11s: for 11 × a single digit, just repeat the digit. 11 × 4 = 44.
- The 6s: an even number times 6 ends in that same number. 6 × 8 = 48, which ends in 8.
- 7 × 8: remember the pattern "5, 6, 7, 8": 56 = 7 × 8.
- Use what you know: if you know 5 × 7 = 35, then 6 × 7 is 35 + 7 = 42.
Multiplying by 11 (two digits)
For 36 × 11: write the outside digits 3 and 6, and put their sum (9) in the middle: 396. If the sum is 10 or more, carry: 58 × 11: 5, (5 + 8 = 13), 8, so carry the 1 to get 638.
Multiplying by 99 or 9
To multiply by 99, multiply by 100 and subtract the number: 47 × 99 = 4,700 − 47 = 4,653. For 9, multiply by 10 and subtract.
Squaring a number that ends in 5
Take the digit(s) before the 5, multiply by the next number up, then write 25 after it. For 35²: 3 × 4 = 12, so the answer is 1,225. For 75²: 7 × 8 = 56, so 5,625.
Adding and subtracting by rounding
To add 48 + 37, think 50 + 37 − 2 = 85. To subtract 83 − 29, think 83 − 30 + 1 = 54. Rounding to a friendly number and adjusting is faster than carrying.
Quick percentages
- 10% of a number: divide by 10. 10% of 250 is 25.
- 5%: half of 10%. 5% of 80 is 4.
- 15%: 10% plus 5%. 15% of 80 = 8 + 4 = 12.
- 25%: a quarter. 50%: half. 1%: divide by 100.
For anything else, use the percentage calculator to check your work.
Divisibility rules
These tell you whether a number divides exactly without doing the division:
| Divisible by | Rule | Example |
|---|---|---|
| 2 | Ends in 0, 2, 4, 6 or 8 | 346 |
| 3 | The digits add up to a multiple of 3 | 1,236 (1+2+3+6 = 12) |
| 4 | The last two digits make a multiple of 4 | 316 (16) |
| 5 | Ends in 0 or 5 | 8,745 |
| 6 | Divisible by both 2 and 3 | 1,236 |
| 8 | The last three digits make a multiple of 8 | 1,208 (208) |
| 9 | The digits add up to a multiple of 9 | 729 (7+2+9 = 18) |
| 10 | Ends in 0 | 4,560 |
| 11 | Alternate adding and subtracting the digits gives 0 or a multiple of 11 | 918,082 (9−1+8−0+8−2 = 22) |
Divisibility rules are very helpful for finding factors and for the LCM and HCF calculator and the prime number checker.
Sum of numbers
To add 1 to 100, pair the numbers: 1 + 100, 2 + 99 and so on. There are 50 pairs of 101, so the total is 5,050. The sum of the first n odd numbers is n²: 1 + 3 + 5 + 7 = 16 = 4².
How to practise
Pick one trick a week, practise it for five minutes a day, then mix it into the quiz. Say the method out loud. If your child is learning tables, start with the easy ones and add the harder ones gradually. If maths feels stuck, our fun maths classes build number sense with puzzles and visual explanations.
Common questions
What is the easiest way to learn times tables?
Little and often, with patterns. Start with the 2s, 5s and 10s, then the 3s, 4s and 9s, then the 6s, 7s and 8s. Say them aloud, and use games and quizzes.
Do these tricks work for adults too?
Yes. Rounding, quick percentages and squaring numbers ending in 5 are handy for shopping, tipping and checking bills.
How can I check my mental maths answers?
Estimate first, and then check with a calculator. For percentages, fractions and interest, use our free calculators that show their working.
Should children learn tricks or understand the method first?
Understanding first, then tricks. A trick without understanding is easy to forget. Each trick here has a simple reason behind it, and asking "why does that work?" is excellent maths.
How long does it take to get faster?
Most children see progress within a couple of weeks of five-minute daily practice. Speed grows with accuracy, so aim for correct first, then quicker.
This guide is general information. For exams, follow your school, teacher and official exam board, and use your own judgement about what suits your child.