Question

The sum of the first n natural numbers is given by _________

(a) n(n+1)/2

(b) n(n-1)/2

(c) n^2(n+1)/2

(d) None of the mentioned

This question was posed to me during an internship interview.

My question comes from Special Sequences in section Basic Structures: Sets, Functions, Sequences, Sums and Matrices of Discrete Mathematics

Answer 1

The correct choice is (a) n(n+1)/2

The explanation is: 1 + 2 + 3 + 4 +……n = (n/2)(1 + n) Since this is AP.