10 Amazing Math Tricks

10 Amazing Math Tricks

1. Multiplying by 11: To multiply a two-digit number by 11, simply add the two digits together and place the result between them. For example, 34 x 11 = 374.

2. Squaring numbers ending in 5: To square a number that ends in 5, simply multiply the first digit by itself plus 1, and then add 25 to the end. For example, 45 x 45 = 2025.

3. Finding percentages: To find a percentage of a number, simply multiply the number by the percentage and then divide by 100. For example, to find 20% of 50, multiply 50 x 20 and then divide by 100 to get 10.

4. Divisibility by 3: A number is divisible by 3 if the sum of its digits is divisible by 3. For example, 435 is divisible by 3 because 4+3+5=12, which is divisible by 3.

5. Divisibility by 9: A number is divisible by 9 if the sum of its digits is divisible by 9. For example, 981 is divisible by 9 because 9+8+1=18, which is divisible by 9.

6. Squaring two-digit numbers ending in 1: To square a two-digit number that ends in 1, take the first digit and multiply it by one more than itself, and then place 1 at the end. For example, 31 x 31 = 961.

7. Dividing by 5: To divide a number by 5, simply multiply it by 2 and move the decimal point one place to the left. For example, to divide 60 by 5, multiply 60 x 2 to get 120, and then move the decimal point one place to the left to get 12.

8. Multiplying by 9: To multiply a number by 9, simply multiply it by 10 and then subtract the original number. For example, to multiply 7 by 9, first multiply by 10 to get 70, and then subtract 7 to get 63.

9. Dividing by 9: To divide a number by 9, add up its digits and keep adding the resulting digits until you get a single digit. If that digit is 9, the original number is divisible by 9. For example, to divide 180 by 9, add 1+8+0=9, which is divisible by 9, so 180 is divisible by 9.

10. Multiplying by 5: To multiply a number by 5, simply divide it by 2 and then multiply by 10. For example, to multiply 24 by 5, first divide by 2 to get 12, and then multiply by 10 to get 120.