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**Ratio and Proportion**

- Always simplify as low as possible.
- Always convert to common units when working out.
- Remove units in final answer.

When it comes to IGCSE/GCSE Maths, can you calculate the ratio of two different units?

- E.g. 500p : £15

- common unit ⟶ £5 : £15

- simplify ⟶ £1 : £3

- final answer ⟶ 1 : 3

**Compound Measures**

- Involves 3 variables.
- These can be connected by a triangle.
- E.g. Pay ⟶ hours worked × rate per hour

- P = H × R

- H = P/R

- R = P/H

**Unit Changes**

- 1m = 100 cm
- 1m² = 10,000cm (100 × 100)
- 1m³ = 1,000,000 cm³ (100 × 100 ×100)

- 1cm² = 100mm²
- 1m² = 10,000 cm²
- 1km² = 1,000,000 m²

- 1cm³ = 1,000 mm³
- 1m³ = 1,000,000 cm³
- 1km³ = 10⁹ m³

- If you go down a unit --> multiplication ×.
- If you go up --> division ÷.

That's the end of the topic!

Drafted by Bonnie (Mathematics)