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JAMB Mathematics 2012 Question 20

Question 20

Progressions

The sum to infinity of a geometric progression is −1/10 and the first term is −1/8. Find the common ratio of the progression.

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

Answer: B (−1/4)

Explanation

−1/10 = (−1/8)/(1 − r), so 1 − r = 10/8 and r = −1/4.