Answer
$1185$
Work Step by Step
$S=25+(25+1)+(25+2)+\cdots+(25+29)$
The terms of the sum form an arithmetic sequence with
$a_{1}=25,d=1,$ and $n=30$
The sum $S_{n}$ of the first $n$ terms of $\left\{a_{n}\right\}$:
$S_{n}=\displaystyle \frac{n}{2}\left[2a_{1}+(n-1)d\right]$
$S_{30}=\displaystyle \frac{30}{2}\left[2(25)+1(29)\right]=15(79)=1185$
