Ratio and proportion
Proportion
A proportion compares a part to the whole. We use the words 'in every' and 'out of', and can write it as a fraction or a percentage.
Finding a proportion
1. Count the part you want. 2. Count the whole (the total). 3. Write it as 'part out of whole', which is a fraction — and you can turn that into a percentage.
Worked examples
As a fraction
- There are 10 blue and 20 red boats — 30 boats in total.
- Blue is 10 out of 30.
Answer: The proportion of blue boats is 1/3.
As a percentage
- A bag has 3 blue counters out of 10.
- 3 out of 10 is the same as 30 out of 100.
Answer: The proportion of blue counters is 30%.
Where you see this in real life
- Saying what fraction of a class chose a favourite colour.
- Describing what proportion of beads on a string are grey.
- Working out what percentage of a recipe is one ingredient.
Key words
- Proportion
- A comparison of a part to the whole (a fraction or percentage).
- Ratio
- A comparison of one part to another part, written a : b.