1.1 Writing a percentage as a fraction or decimal

Fractions, decimals and percentages are all interchangeable, so you can choose to use whichever is most appropriate for your situation. From the definition of a percentage, 75 per cent means 75 out of 100. This can therefore be written as [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] , which can be simplified as . Alternatively, means , or 0.75. So, .

You can see from the pizzas below that dividing them into and , or 25% and 75%, or 0.25 and 0.75, always amounts to the samething.

Figure 3 Pizza maths

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Three circles each with a quarter cut out. Each quarter is labelled ‘one quarter,’ ‘twenty five per cent,’ and ‘0.25’ respectively

Figure 3 Pizza maths

Since dividing a number by 100 has the same effect as moving its decimal point two places to the left, you have a valuable shortcut when you turn a percentage into a decimal. [Looking for the decimal point in a whole number? Remember, the decimal point can be inserted at the end of your number behind the units place.]

For example: 6% = .