Question

Find the sum:
$34+32+30+......+10$

Answer 1

In the given series $34+32+30+......+10$ the first term is $34$ and common difference is $-2$.

Let us assume there are $n$ terms.

Then $n$ th term is $10$.

Then $34+(n-1)(-2)=10$

or, $-2(n-1)=-24$

or, $n=13$.

Now the sum of the series is

$=\frac{13}{2}(10+34)$

$=286$.