Unequal sharing
In a nutshell
Ratios can be used in lots of different scenarios - one of the most common being when things are shared unequally.
Ratio vs proportion
Definitions
Ratio
| Compares one part to another.
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Proportion
| Compares one part to the whole thing
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Example 1
Look at the squares.
The ratio of shaded to unshaded squares can be written:
3:1
The proportion of shaded squares is three (the number shaded) out of four (the total number of squares). Written as a fraction: 43
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Unequal sharing problems
When things are shared unequally, ratios and proportions can both be used to work out how many things each person gets.
Example 2
For every one slice of pizza that Rachel eats, her older sister Anna eats two. There are six slices in a whole pizza. Work out how many each of them get and write your answer as a ratio.
Write the information as a ratio.
Rachel : Anna
1:2
Add up the ratio and work out the proportion eaten by each person.
1+2=3
Rachel eats a third: 31
Anna eats two thirds: 32
Work out each fraction of the total amount to find out how much eat person gets.
Rachel: 31 of 6=6÷3=2
Anna: 32 of 6=(6÷3)×2=4
Therefore, Rachel and Anna get pizza in a ratio of 2:4.
Note: The numbers in the ratio should be given in the same order as the words in the question. Rachel is listed first, so her number in the ratio comes first.