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0580/22 Feb/Mar 2021, Question 22: Calculating with Bounds

Cambridge IGCSE Mathematics 0580 · Paper 22 (Extended) · Calculator · 4 marks

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The question, in short

Use rounded measurements of a 25 kg rice bag and 200 m of wire cut into 3 m pieces to work out a lower bound and a maximum number of pieces.

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

Part (a) · 1 mark

Find the smallest possible total mass of 10 bags, given each bag's mass is 25 kg to the nearest kilogram.

  1. 1Lower bound of one bag = 25 − 0.5 = 24.5 kg
  2. 2Lower bound of 10 bags = 10 × 24.5 = 245 kg

Answer245

Part (b) · 3 marks

Find the greatest number of 3 m pieces (to the nearest 20 cm) that can be cut from 200 m of wire (to the nearest metre).

  1. 1Most wire: upper bound = 200 + 0.5 = 200.5 m
  2. 2Shortest piece: lower bound = 3 − 0.1 = 2.9 m
  3. 3200.5 ÷ 2.9 = 69.1…
  4. 4Largest possible n = 69

Answer69

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