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JAMB Mathematics 2004 Question 19

Question 19

Progressions

Given that the first and fourth terms of a G.P. are 6 and 162 respectively, find the sum of the first three terms of the progression.

  1. A.8
  2. B.27
  3. C.48
  4. D.78
Show the answer and explanation

Answer: D (78)

Explanation

ar3 = 162 and a = 6, so r3 = 27 and r = 3. The first three terms are 6, 18, 54, which add to 78.