What is the sum of the first 17 terms of an arithmetic progression if the first term is -20 and last term is 28?

Solution (By Examveda Team)

First term of AP = a = -20 and last term = l = 28
Number of terms = n = 17
$$\eqalign{ & {\text{Sum of AP}} = \frac{{\text{n}}}{2}\left( {{\text{a}} + {\text{l}}} \right) \cr & = \frac{{17}}{2}\left( { - 20 + 28} \right) \cr & = 17 \times 4 \cr & = 68 \cr} $$