The sum of the first n terms of an arithmetic progresssion is 252. If the…

Mathematics JAMB 2003

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

  • 6
  • 7
  • 8
  • 9 checkmark

The correct answer is: D

Explanation

\(S_n = 252, a = -16\hspace{1mm}and\hspace{1mm}l = 72\\S_n = \frac{n}{2}(-16+72)\\252 = \frac{n}{2}(-16+72)\\n=\frac{504}{56}\\n=9\)
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