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0580/43 Oct/Nov 2024, Question 3: Simple Interest

Cambridge IGCSE Mathematics 0580 · Paper 43 (Extended) · Calculator · 9 marks

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The question, in short

Three investment problems: find a simple interest rate, compound interest earned, and a monthly compound rate from given amounts, times and final values.

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

Part (a) · 3 marks

Ed's $500 grows to $675 over 14 years with simple interest at r% per year; find r.

  1. 1Interest = 675 − 500 = $175
  2. 2500 × r/100 × 14 = 175
  3. 370r = 175
  4. 4r = 2.5

Answer2.5

Part (b) · 3 marks

Eva invests $400 at 2.2% per year compound interest; calculate total interest earned after 11 years.

  1. 1Amount = 400 × 1.022¹¹
  2. 2= 508.18...
  3. 3Interest = 508.18 − 400 = $108.18

Answer108.18

Part (c) · 3 marks

Erin's $700 grows to $1074 over 21 years with monthly compound interest at p%; find p.

  1. 121 years = 12 × 21 = 252 months
  2. 2700 × (1 + p/100)²⁵² = 1074
  3. 31 + p/100 = (1074/700)^(1/252) = 1.001700...
  4. 4p = 0.170

Answer0.170 or 0.17 or 0.1700…

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Also searched as: 0580/43/O/N/24 · 0580_w24_qp_43 · 0580 w24 43 · question 3.
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