# Simple Maths Hacks

## 1. Multiplying big numbers together (less than 100) ## 2. How to learn the value of π to 7 decimal places ## 3. Finger multiplication (6-10) Example: 7x8 = 56

1. Rotate one hand to the finger of 7

2. Rotate the other hand to the finger of 8

3. Count the number of fingers below and including the fingers touching. This is the tens number (e.g. 5 fingers = 50)

4. Then multiply the fingers that are above and add them to the tens number (e.g. 3 fingers on one hand multiplied by 2 fingers on the other = 6)

## 4. Multiplying numbers by 11 If the sum of the two numbers is 10 or more add the tens digit to the number on the far left (e.g. 59 x 11 = 649 (5+9 = 14, 1+5=6)

## 5. Subtracting numbers from 1000 easily

Subtract all digits from 9 except the last one. And subtract the last digit from 10. Combine the answers in order and you get your answer.

Example: 1000 - 795 = ?

Split the numbers up and subtract the first few from 9 and the last from 10

First step = 9 - 7 = 2

Second step  = 9 - 9 = 0

Third step = 10 - 5 = 5

Last step = Then recombine the numbers

1000 - 795 = 205

## 6. Quick Square Calculation (finding the square of a two-digit number that ends with 5) ## 7. Difficult multiplication made easy

To make the multiplication easy, half the first number and double the second until there is a straightforward calculation  ## 8. Division by 5 