Question

Find the sum: $(-5)+(-8)+(-11)+.....+(-230)$

Answer 1

It is an A.P.,

in which, $a=-5,d=-8-(-5)=-3,l=-230$

First calculate the number in series.....

$l=a+(n-1)d$

$-230=-5+(n-1)-3$

$-225=-3n+3$

$3n=228$

$n=76$.

Now,

Sum of the series $=\frac{n}{2}(a+l)$

$76/2(-5-230)$

$38\times -235=-8930$.

So, the sum of your series would be $-8930$.