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4MA1/2F Jan 2022, Question 18: Similar Triangles

Pearson Edexcel International GCSE Mathematics A 4MA1 · Paper 2F (Foundation) · Calculator · 3 marks

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The question, in short

Use similar triangles ABC and PQR with AB = 4 cm, PQ = 12 cm, RQ = 16.5 cm to find BC and relate AC = x to PR = y.

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

Part (a) · 2 marks

Calculate side BC of the smaller triangle using the scale factor from the given corresponding sides.

  1. 1Scale factor = PQ ÷ AB = 12 ÷ 4 = 3
  2. 2BC matches RQ, so BC = 16.5 ÷ 3 = 5.5

Answer5.5

Part (b) · 1 mark

Express PR, labelled y, as an expression involving AC, labelled x, using similarity.

  1. 1Scale factor = PQ ÷ AB = 12 ÷ 4 = 3
  2. 2PR matches AC, so y = 3x

Answer3x

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