For any +ve integer n, the sum of the first n +ve integers equals n(n+1)/2. What is the sum of all the even integers between 99 and 300.
a.10,100
b.20,200
c.22,650
d.40,200
e.45150

b

by subtracting the sum of first 99 and sum of first 300. it is very clear that we can eliminate a,d,e.
I had to choose between b and c.
the option c is to from half of the value obtained above. so i choose b.

Is there is any better way of doing this?

Is there is a way to find sum of even numbers?