Question

Which of the following is a Triangular number series?

(a) 1, 3, 6, 9, 12, 15…..

(b) 1, 3, 6, 10, 15, 21……

(c) 1, 6, 12, 18, 24…..

(d) none of the mentioned

This question was posed to me in a national level competition.

This interesting question is from Special Sequences in division Basic Structures: Sets, Functions, Sequences, Sums and Matrices of Discrete Mathematics

Answer 1

Correct answer is (b) 1, 3, 6, 10, 15, 21……

To explain I would say: In triangular number sequence ith term is previous term+i, with first term as 1.