# Maths:Indices and Standard Form

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• Created by: Wunmi
• Created on: 29-10-10 14:44

### Indices

#### Powers and Roots

power tells you to multiply a number by itself.

For example, 53 means 5 x 5 x 5 which is 125.

24 means 2 x 2 x 2 x 2 which is 16.

It is a short way of writing out calculations.

For example, 33 x 42 = 3 x 3 x 3 x 4 x 4 = 432

root is the opposite of a power.

For example:

- means 'what number do you square to get 4?'

- means 'what number do you cube (multiply by itself 3 times) to get 27?'

#### Rules of indices

There are several rules that you will need to know.

Rule 1

When you multiply indices of the same number you add the powers.

For example: 54 x 53 = 54 + 3 = 57

Rule 2

When you divide indices of the same number you subtract the powers.

Rule 3

Indices outside a bracket multiply.

For example: (324 = 32 x 4 = 38

Rule 4

Negative indices mean reciprocal, i.e. 'one over...' or 'put on the bottom of a fraction'.

Rule 5

When the power is a fraction the top of the fraction (numerator) is a power and the bottom of the fraction…