GMAT Quantitative Reasoning Practice Test 2

The sum of the even integers between 30 and 50 inclusive can be calculated using the product of the number of integers by their average. The average of a fixed-difference sequence of numbers can be calculated as the average of the largest and the smallest numbers:
$\frac{\left(30+50\right)}{2}=40$
We remember that between 30 and 49 , inclusive, there are 20 numbers of which half are even and half odd. Add 1 (the number 50 ) to the 10 even numbers to receive a total of 11 even integers, multiply it by the average to get the sum: $40\times 11=440$.