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Year 9
Ratio & Proportion
Definition
Simplifying a ratio means dividing all its parts by a common factor, keeping the same relationship. A ratio is in its simplest form when the parts share no common factor.
Why Do I Have to Learn This?
Ratios compare amounts, like squash to water or flour to butter. Getting proportions right is how recipes, maps and models work.
Key Rules:
- 1. Divide every part by a common factor.
- 2. Keep dividing until no common factor remains.
- 3. The order of the parts stays the same.
Remember:
- •10 : 15 divides by 5 to give 2 : 3.
- •A ratio simplifies like a fraction.
- •Units must match before simplifying.
Direct proportion
Two quantities that change together: double one and the other doubles too. y = kx for a fixed number k.
If 1 apple costs 30p, then 4 apples cost 120p.
Animated Example:
:
2 blue to 3 green is 2 : 3
Free Ratio & Proportion Worksheet
Download free worksheets and practise today.
Every download has a fresh set of questions.
Let’s Practise the Concept
Step 1 of 3
Put them in order
Tap the numbers from smallest to largest.
In order so far: nothing yet