Question

Find the sum of the following $AP$.
$2,7,12,....,$ to $10$ terms

Answer 1

Sum of A.P.

$=\frac{n}{2}(2a+(n-1\left)d\right)$

Given that,

$n=10,a=2,d=7-2=5$

put the values

$sum=\frac{n}{2}(2a+(n-1\left)d\right)$

$=\frac{10}{2}(2\times 2+(10-1)\times 5)$

$=245$