Question

The sum of terms upto $10$ terms of series $12,15,18,21,24,27,.......$

Answer 1

The series is $12,15,18,21,24,27,...$

The series is In AP

With $a=12,d=3$

$S_{10}=\frac{10}{2}\left(2\right(12)+(10-1\left)\right(3\left)\right)5(24+27)=255$