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WMA12/01 Jan 2025, Question 1: Arithmetic Progressions in Problems

Pearson Edexcel International AS Level Mathematics · Pure Mathematics 2 (WMA12) · Calculator · 4 marks

The question, in short

For the arithmetic series 2 + 5 + 8 + 11 + … + 254, find how many terms it contains and the total sum of the series.

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Part (a) · 2 marks

Find the number of terms in the arithmetic series 2 + 5 + 8 + 11 + … + 254.

  1. 1First term a = 2, common difference d = 3, last term 254
  2. 2254 = 2 + 3(n − 1)
  3. 33(n − 1) = 252, so n − 1 = 84
  4. 4n = 85

Answer85 terms

Part (b) · 2 marks

Find the sum of the arithmetic series 2 + 5 + 8 + 11 + … + 254.

  1. 1S = n/2 (a + l)
  2. 2S = 85/2 × (2 + 254)
  3. 3S = 85/2 × 256
  4. 4S = 10 880

Answer10 880

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