A problem by anweshan bor

This describes the sum of the first $180$ terms of the arithmetic sequence with first term $a_1 = 103$ and common difference $d = 5$ . The sum is given by:

$S_{180} = \frac{180}{2}(a_1 + a_{180}) = 90(103 + 998) = \boxed{99 090}$

According to the question, the series is 103,108,113.... 998 Find the n digits by (l-a/d)+1 Using sum of series formula n/2(2a+(n-1)d) we get the answer