Free practice on Interest, Rate and Proportion for Class 6, following the Cameroon primary school curriculum (English subsystem). Every answer is explained, so a parent who is not sure of the answer can still help.
I = P × R × T ÷ 100. P = principal (money). R = rate percent per year. T = time in years. 10,000 F at 6% for 3 years: I = 10,000 × 6 × 3 ÷ 100 = 1,800 F.
Direct: both grow together (more items → more cost). Inverse: as one grows, the other shrinks (more workers → less time). Use ratios to solve both.
| Type | Rule | Example |
|---|---|---|
| Direct | As one grows, the other grows | 1 pen 200 F, 5 pens 1,000 F |
| Inverse | As one grows, the other shrinks | 3 workers 6 days → 6 workers 3 days |
Compound proportion mixes both. Example: 3 workers finish 6 items in 4 days. How many days for 6 workers to finish 12 items? Break into steps.
Find the simple interest: Principal = 50,000 FCFA, Rate = 4%, Time = 2 years. Interest in FCFA = ?
Write your answer, then check below.
Answer: 4000
I = P × R × T ÷ 100 = 50000 × 4 × 2 ÷ 100 = 4000 FCFA.
An interest of 2000 FCFA is earned on 10,000 FCFA in 2 years. What was the rate? (answer in %)
Write your answer, then check below.
Answer: 10
R = 100 × I ÷ (P × T) = 100 × 2000 ÷ 20000 = 10%.
5 metres of cloth cost 7500 FCFA. How much do 8 metres cost in FCFA?
Write your answer, then check below.
Answer: 12000
1 m = 1500 FCFA, so 8 m = 12,000 FCFA.
6 workers can dig a farm in 12 days. How many days will 4 workers take?
Write your answer, then check below.
Answer: 18
Inverse proportion: 6 × 12 = 72, then 72 ÷ 4 = 18 days.
A moto uses 3 litres of fuel for 60 km. How many litres for 100 km?
Write your answer, then check below.
Answer: 5
60 ÷ 3 = 20 km per litre, then 100 ÷ 20 = 5 litres.
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