Answer
9150
Work Step by Step
Answer = 5 + 10 + 15 + 20 + ··· + 300
= $5\times(1+2+3+4+ ... + 60)$
Now,
1+2+3+4+ ... +60 = $\frac{60\times(60+1)}{2}$ = 1830
as, 1+2+3+ ... +n = $\frac{n\times(n+1)}{2}$
Therefore,
Answer = $5\times1830$ = 9150