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WAEC Mathematics 1991 (August) Question 23

Question 23

Progressions

The common ratio of a G.P. is 2. If the 5th term is greater than the 1st term by 45, find the 5th term,

  1. A.3
  2. B.6
  3. C.45
  4. D.48
  5. E.90
Show the answer and explanation

Answer: D (48)

Explanation

ar4 − a = 16a − a = 15a = 45, so a = 3 and the 5th term = 3 × 16 = 48.