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4024/22 Oct/Nov 2024, Question 4: Earnings and Deductions

Cambridge O Level Mathematics 4024 · Paper 22 (Calculator) · Calculator · 8 marks

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The question, in short

Work through three money problems: find a shirt price from change, compare a camera price in dollars and euros, and find a compound interest rate.

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

Part (a) · 3 marks

Anya buys 4 shirts and 3 hats at $13.50 each, pays $100 and gets $21.50 change. Find the cost of one shirt.

  1. 1Spent = 100 − 21.50 = $78.50
  2. 2Hats = 3 × 13.50 = $40.50
  3. 34 shirts = 78.50 − 40.50 = $38, so one shirt = 38 ÷ 4 = $9.50

Answer9.50

Part (b) · 2 marks

Using $1 = €0.91, convert a $150 camera price and a €140 online price, then find the difference in dollars to the nearest cent.

  1. 1€140 in dollars = 140 ÷ 0.91 = $153.846…
  2. 2Difference = 153.846… − 150 = $3.846… ≈ $3.85

Answer3.85

Part (c) · 3 marks

$600 is invested at r% compound interest per year; after 3 years interest totals $21.86. Calculate r.

  1. 1600 × k³ = 600 + 21.86 = 621.86
  2. 2k = ∛(621.86/600) = 1.012
  3. 3r = 1.2

Answer1.2

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