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4MA1/2F Jan 2022, Question 19: Upper and Lower Bounds

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

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The question, in short

A regular octagon has side length 18 mm measured to the nearest 0.5 mm; state the lower and upper bounds of the side length.

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

Part (a) · 1 mark

Give the smallest possible value of the side length consistent with 18 mm rounded to the nearest 0.5 mm.

  1. 1The length is 18 mm, correct to the nearest 0.5 mm.
  2. 2So the smallest possible value is halfway between 17.5 and 18, which is 17.75.

Answer17.75

Part (b) · 1 mark

Give the largest possible value of the side length consistent with 18 mm rounded to the nearest 0.5 mm.

  1. 1The length is 18 mm, correct to the nearest 0.5 mm.
  2. 2So the largest possible value is halfway between 18 and 18.5, which is 18.25.

Answer18.25

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