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0580/41 May/Jun 2021, Question 4: Compound Interest

Cambridge IGCSE Mathematics 0580 · Paper 41 (Extended) · Calculator · 9 marks

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The question, in short

Currency conversion, proportion and compound interest problems: convert $500 to euros, compare computer prices in dollars, find savings from a fraction spent, and find the annual rate r.

Summarised in our own words. Use the official paper for the exact wording and any diagrams.

Part (ai) · 2 marks

Change $500 into euros at 1 euro = $1.142, giving the answer to the nearest euro.

  1. 1500 ÷ 1.142 = 437.8…
  2. 2≈ 438 euros

Answer438

Part (aii) · 2 marks

A computer costs $329 or 275 euros; find the difference in cost in dollars.

  1. 1275 euros = 275 × 1.142 = $314.05
  2. 2Difference = 329 − 314.05 = $14.95

Answer14.95

Part (b) · 2 marks

A book costing $5.25 is 3/8 of Lucy's savings; calculate her total savings this month.

  1. 13/8 of savings = 5.25
  2. 2Savings = 5.25 × 8/3 = $14

Answer14

Part (c) · 3 marks

$6130 grows at r% compound interest to $6669 over 5 years; calculate r.

  1. 16130 × (1 + r/100)⁵ = 6669
  2. 21 + r/100 = ⁵√(6669 ÷ 6130) = 1.01699…
  3. 3r = 1.699… ≈ 1.70

Answer1.70 or 1.699…

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