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WAEC Further Mathematics 2019 Question 16

Question 16

Sequences and Series

The second and fourth terms of an exponential sequence (G.P.) are 2/9 and 8/81 respectively. Find the sixth term of the sequence

  1. A.81/32
  2. B.9/8
  3. C.1/4
  4. D.32/729
Show the answer and explanation

Answer: D (32/729)

Explanation

r² = (8/81) ÷ (2/9) = 4/9, so r = 2/3 and a = 1/3. T₆ = ar⁵ = (1/3)(32/243) = 32/729.