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WAEC Mathematics 1996 Question 1

Question 1

Progressions

The 6th term of a G.P. is −2/27 and its first term is 18. What is the common ratio?

  1. A.−½
  2. B.−1/3
  3. C.1/4
  4. D.2
  5. E.3
Show the answer and explanation

Answer: B (−1/3)

Explanation

The 6th term is ar5, so 18r5 = −2/27, giving r5 = −1/243. The fifth root of −1/243 is −1/3.