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0606/12 Feb/Mar 2026, Question 4: Arithmetic Progressions in Problems

Cambridge IGCSE Additional Mathematics 0606 · Paper 12 (Non-calculator) · Non-calculator · 3 marks

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The question, in short

An arithmetic progression has common difference −2 and equal sums for the first 4 and first 10 terms. Find the first term.

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Solution · 3 marks

  1. 1S₄ = (4/2)(2a + 3(−2)) = 4a − 12
  2. 2S₁₀ = (10/2)(2a + 9(−2)) = 10a − 90
  3. 34a − 12 = 10a − 90
  4. 46a = 78, a = 13

Answer13

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