Question

In an A.P. the first term is $2$, the last term is $29$, and the sum is $155$, then find the common difference.

Answer 1

Given $a=2,l=9$ and $S=155$

$S=\frac{n}{2}(a+l)155=\frac{n}{2}(2+29)\Rightarrow n=10l=a+(n-1)d29=2+(10-1)d\Rightarrow d=3$

So the common difference is $3$