Find the sum of the following APs:
$-37, -33, -29$ …… to $12$ terms.

Given AP is $-37, -33, -29$ ……

To do:

We have to find the sum of the given A.P. to 12 terms.

Solution:

$a=-37, d=-33-(37)=-33+37=4, n=12$

We know that,

$S_{n}=\frac{n}{2}[2 a+(n-1) d]$

$S_{12}=\frac{12}{2}[2 \times(-37)+(12-1) 4]$

$=6(-74+44)$

$=6 \times(-30)$

$=-180$