Ratio & Rate
Solve problems involving ratio and rate
Ratio and Rate
A ratio compares two quantities of the same kind (e.g. boys to girls = 3:5). A rate compares two quantities of different kinds (e.g. km per hour, rands per kg).
Example
Working with Ratio
Share R120 in the ratio 2:3.
Total parts = 2 + 3 = 5
One part = R120 ÷ 5 = R24
First share = 2 × R24 = R48
Second share = 3 × R24 = R72
Check: R48 + R72 = R120 ✓
Example
Working with Rate
A car travels 240 km in 3 hours.
Rate = 240 ÷ 3 = 80 km/h
A shop sells apples at R15 per kg.
3 kg costs: 3 × R15 = R45
Note
Remember
Ratio: same type of unit (boys:girls, litres:litres). Rate: different units (km/h, R/kg). Always include units when writing a rate.
Key Vocabulary
RatioA comparison of two amounts of the same type
RateA comparison of two amounts with different units
SpeedDistance divided by time (km/h)
Unit rateA rate with denominator 1 (e.g. R5 per item)
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Ratio
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