What is the sum of the sequence: 2+4+6+…+98+100=?

(A) 2450
(B) 2500
(C) 2550
(D) 2600

The answer is: (C) 2550
Solution
This is an arithmetic sequence with common difference of 2. The first element is 2, the last element is 100, and total elements (from 2 to 100) are 50. So, a₁ = 2, a_n = 100, d = 2 and n = 50. So, by using the formula for the sum of n elements of an arithmetic sequence, we have