If x is equal to the sum of the even integers from 40 to 60 inclusive, and y is the number of even integers from 40 to 60 inclusive, what is the value of x+y?	Choose the correct choice from the following answers.
A) 550	B) 551	C) 560	D) 561	E) 572
This is a perfect example of why you should not use formulas without understanding them properly. If you understand them, you will not make a mistake and will save time.   The formula quoted by the original poster: n(n+1) is absolutely fine. But one needs to understand that n is the number of even terms starting from the first even term. (I discuss why this is so here:   Sum of even numbers from 40 to 60 using this formula will be:   30*31 - 19*20 = 10(3*31 - 19*2) = 550   Since number of terms is 11, required sum is 561   But, I would not use this formula for this question and would do it the way many of you have done:   Average = 50 (it is the middle number), Number of terms = 11 (No formula again. Any 10 consecutive integers have 5 even and 5 odd numbers. 41 to 60 will have 10 even integers and 40 is the 11th one)   Sum = 50*11 + 11= 
<gadget id="calculator">50*11 + 11</gadget>
<output>561</output>
561   answer is 561
<result>D</result>
If x is equal to the sum of the even integers from 40 to 60 inclusive, and y is the number of even integers from 40 to 60 inclusive, what is the value of x+y?