A ratio is used to compare two quantities which are measured in the same units. Given a ratio, quantities can be calculated.
Part of Application of MathsNumeracy skills
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Follow this example of splitting a quantity in a given ratio.
\(\pounds30\) is shared between Ken and John in the ratio \(2 : 1\). How much does each get?
If something is split in the ratio \(2 : 1\), then there are 3 'parts' altogether.
1 part \(= \frac{{30}}{3} = \pounds10\)
Ken has 2 parts \(= 2 \times \pounds10 = \pounds20\)
John has 1 part \(= 1 \times \pounds10 = \pounds10\)
Use the same method of working to solve this question.
There are 180 pupils in a school year.
The ratio of left handed pupils to right handed pupils is \(1 : 8\).
How many pupils are right handed?
The ratio is \(1 : 8\) so there are 9 'parts' altogether.
1 part\( = \frac{{180}}{9} = 20\)
Left-handed pupils \(= 1 \) part \(= 1 \times 20 = 20\)
Right-handed pupils \(= 8 \) parts \(= 8 \times 20 = 160\)