Maths Hacks – Learn Fast Techniques to Solve Maths Problems Like a Pro

Explore these fun math tricks to simplify calculations, check divisibility, and improve mental math skills! Each trick is designed to make math faster and more enjoyable.

1. Divisibility by 2

If a number ends in an even digit (0, 2, 4, 6, or 8), it is divisible by 2.

Example: 28 ends in 8, so it’s divisible by 2.
Example: 46 ends in 6, so it’s divisible by 2.

2. Divisibility by 3

If the sum of all the digits of a number is divisible by 3, then the number itself is divisible by 3.

Example: 123, sum of digits is 1 + 2 + 3 = 6, which is divisible by 3.
Example: 453, sum of digits is 4 + 5 + 3 = 12, divisible by 3.

3. Divisibility by 4

If the last two digits of a number form a number divisible by 4, then the entire number is divisible by 4.

Example: 132, last two digits are 32, which is divisible by 4.

4. Divisibility by 5

If a number ends in 0 or 5, it is divisible by 5.

Example: 35 and 120 both end in 5 or 0, so they’re divisible by 5.

5. Divisibility by 6

A number is divisible by 6 if it is divisible by both 2 and 3.

Example: 54 is even (divisible by 2) and 5 + 4 = 9 (divisible by 3). So, 54 is divisible by 6.

6. Divisibility by 9

If the sum of all the digits of a number is divisible by 9, then the number itself is divisible by 9.

Example: 729, sum of digits is 7 + 2 + 9 = 18, divisible by 9.

7. Multiplying by 5

To multiply by 5 quickly, divide the number by 2 and then multiply by 10.

Example: 36 × 5, divide by 2 to get 18, then multiply by 10 to get 180.

8. Multiplying by 11

To multiply a two-digit number by 11, add the digits and place the sum in between.

Example: 23 × 11, add 2 + 3 = 5 and place it between 2 and 3 to get 253.

9. Multiplying by 9

To multiply by 9, multiply by 10 and subtract the original number.

Example: 8 × 9, calculate 8 × 10 = 80, then 80 - 8 = 72.

10. Squaring Numbers Ending in 5

Square any two-digit number ending in 5 by multiplying the first digit by itself +1, and add 25.

Example: 45², 4 × 5 = 20, add 25 to get 2025.

11. Divisibility by 8

If the last three digits of a number are divisible by 8, the whole number is divisible by 8.

Example: 1000, last three digits are 000, divisible by 8.

12. Multiplying by 25

To multiply by 25, divide by 4 and then multiply by 100.

Example: 16 × 25, divide by 4 to get 4, then multiply by 100 to get 400.

13. Finding 10% of a Number

To find 10% of a number, simply move the decimal point one place to the left.

Example: 250, 10% is 25.

14. Divisibility by 7

Double the last digit, subtract it from the rest of the number, and if the result is divisible by 7, then the original number is too.

Example: 203, double the last digit (3 × 2 = 6), 20 - 6 = 14, divisible by 7.

15. Divisibility by 10

If a number ends in 0, it is divisible by 10.

Example: 130 ends in 0, so it’s divisible by 10.

16. Adding 9 Quickly

To add 9, add 10 and subtract 1.

Example: 56 + 9, add 10 to get 66, then subtract 1 to get 65.

17. Divisibility by 11

If the difference between the sum of the digits in odd and even positions is 0 or divisible by 11, the number is divisible by 11.

Example: 121, difference is |1 - 2 + 1| = 0, so it’s divisible by 11.

18. Multiplying by 15

To multiply by 15, multiply the number by 10 and add half of the result.

Example: 40 × 15, calculate 40 × 10 = 400, then add half (200) to get 600.

19. Subtracting from 1000

To subtract a number from 1000, subtract each digit from 9, except the last digit from 10.

Example: 1000 - 356, subtract each digit from 9 except the last: 644.

20. Finding 20% of a Number

To find 20%, find 10% and then double it.

Example: 150, 10% is 15, double it to get 30.