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4MA1/2F Jan 2023, Question 20: Estimation

Pearson Edexcel International GCSE Mathematics A 4MA1 · Paper 2F (Foundation) · Calculator · 4 marks

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The question, in short

A 2.75 kg cake weight is given to 2 decimal places; find its bounds, then use one-significant-figure rounding of 81.3 × 59.2 ÷ 1.9² to estimate and check Penny's 13 332.299 17.

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

Part (a) · 1 mark

State the lower bound of the cake weight, given 2.75 kg correct to 2 decimal places.

  1. 12.75 is correct to 2 decimal places, so the true weight is within 0.005 of it
  2. 2The lower bound is 2.75 − 0.005 = 2.745 kg

Answer2.745

Part (b) · 1 mark

State the upper bound of the cake weight, given 2.75 kg correct to 2 decimal places.

  1. 1The upper bound is 2.75 + 0.005 = 2.755 kg

Answer2.755

Part (c) · 2 marks

Round 81.3, 59.2 and 1.9 to one significant figure, then estimate 81.3 × 59.2 ÷ 1.9² and show working.

  1. 181.3 to 1 significant figure is 80
  2. 259.2 to 1 significant figure is 60
  3. 31.9 to 1 significant figure is 2
  4. 4(80 × 60) ÷ 2² = 4800 ÷ 4 = 1200
  5. 51200 is nowhere near 13 332, so her answer is not sensible

Answer1200

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