Find the wrong number in the series.

1, 2, 6, 15, 31, 56, 91

A) 31	B) 15
C) 56	D) 91

Answer: D) 91

Explanation:

The difference of the two consecutive numbers are 1, 4, 9, 16, 25, 35.

This is clearly , $+ (1^{2}), + (2^{2}), + (3^{2}), + (4^{2}), + (5^{2}), + (6^{2})$

Here 35 is wrong, So our wrong number is 91

Subject: Number Series