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JAMB Mathematics 1990 Question 27

Question 27

Progressions

Find the sum of the first twenty terms of the arithmetic progression log a, log a2, log a3, .......

  1. A.log a20
  2. B.log a21
  3. C.log a200
  4. D.log a210
Show the answer and explanation

Answer: D (log a210)

Explanation

The terms are log a, 2 log a, 3 log a, … so the sum is (1 + 2 + … + 20) log a = 210 log a = log a210.