Question

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

Answer 1

We have,

$2,7,12,...........to10$ term

We know that,

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

Here $n=10$,$a=2$,

&$d=7-2=5$

Putting these in formula,

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

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

$=\frac{10}{2}\left(4+9\times 5\right)$

$=5\left(4+45\right)$

$=5\times 49$

Then,

We get $=245$