Question

Find the wrong number in the series.
1, 2, 6, 15, 31, 56, 91

• A. 31
• B. 15
• C. 56
• D. 91

Answer 1

Answer: (D)

91

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