Introduction to percentagesCalculating percentage using the decimal method
Per cent means 'per 100'. If 70 per cent of the population own a pet, this means that 70 out of every hundred people own a pet. The symbol % means 'per cent'.
Another way to find a percentage of an amount is to use the fact that dividing by 100 is the same as multiplying by 0.01.
You can use this method to find any percentage. For example:
\(1%\) of \(400\). Multiply \(400 \times 0.01 = 4\).
\(2%\) of \(400\). Multiply \(400 \times 0.02 = 8\).
\(30%\) of \(400\). Multiply \(400 \times 0.30 = 120\).
This is called the decimal method. If you can turn a percentage into a decimal in your head – for instance by imagining it as pennies in the pound – this method is quick on a calculator as it is only one step.
Question
Q1. In a class of \({25}\) pupils, \(24\%\) live in a flat. How many pupils live in a flat?
\(24\%\) is equivalent to \(0.24\)
\(0.24 \times 25 = 6\)
Therefore \(6\) pupils live in a flat.
Question
Last year Sam earned \(£20,000\). This year her pay has increased by \(8\%\).
a) By how much money has Sam's pay increased?
b) What is her new salary?
a) \(8\%\) of \(20,000 = 0.08 \times 20,000\) \( = 1,600\)
