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UI Post-UTME Mathematics 2023 (Model questions) Question 12

Question 12

Progressions

The sum of the first n terms of geometric progression is given by Sn = 15(2n − 1). What is the common ratio of the progression?

  1. A.2
  2. B.3
  3. C.4
  4. D.5
Show the answer and explanation

Answer: A (2)

Explanation

This matches Sₙ = a(rⁿ − 1)/(r − 1) with r = 2 (and a = 15). Check: T₁ = 15, T₂ = S₂ − S₁ = 45 − 15 = 30.