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JAMB Mathematics 2003 Question 22

Question 22

Progressions

The sum of the first n terms of an arithmetic progression is 252. If the first term is −16 and the last term is 72, find the number of terms in the series.

  1. A.6
  2. B.7
  3. C.8
  4. D.9
Show the answer and explanation

Answer: D (9)

Explanation

S = n/2 (a + l): 252 = n/2 (−16 + 72) = 28n, so n = 9.