Question

Find the sum of $-37,-33,-29,..$ to $12$ terms

• A. $-180$
  
• B. $-210$
• C. $-360$
• D. $-390$

Answer 1

The correct option is A $-180$

The given series is $-37,-33,-29,.........$ to $12$ terms

The given sequence is an AP with first term $a=-37$, common difference $d=4$ and $n=12$.

$\therefore S_n=\frac{n}{2}[2a+(n-1\left)d\right]$
$\therefore S_{12}=\frac{12}{2}[2a+(12-1\left)d\right]$

$=6[2\times -37+11\times 4]$

$=-180$