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0580/11 Oct/Nov 2021, Question 15: Estimation

Cambridge IGCSE Mathematics 0580 · Paper 11 (Core) · Calculator · 2 marks

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The question, in short

Estimate the total price of 73 books costing $21.95 each by rounding both values to 1 significant figure, then judge whether that estimate is above or below the true total without calculating it.

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

Part (a) · 1 mark

Round 73 and 21.95 each to 1 significant figure and multiply to estimate the overall cost.

  1. 173 ≈ 70 and 21.95 ≈ 20
  2. 270 × 20 = $1400

Answer1400

Part (b) · 1 mark

State if 70 × 20 = 1400 is more or less than the actual cost, justifying by comparing rounded values with originals.

  1. 173 was rounded down to 70 and 21.95 was rounded down to 20
  2. 2So the estimate is less than the exact cost, because both values were rounded down

AnswerLess than because both values rounded down

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Also searched as: 0580/11/O/N/21 · 0580_w21_qp_11 · 0580 w21 11 · question 15.
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