What is the sum of the numbers: 1, 2, 3, 4, …, 99, 100?

(A) 5000
(B) 5050
(C) 5100
(D) 5150

The answer is: (B) 5050
Solution
These are the first 100 natural numbers (n=100). So, by applying formula for the sum of the first n natural numbers, we have