Find the wrong number in the following series.
6, 12, 21, 36, 56, 81

Correct option is D

Let's analyze the given series:
6, 12, 21, 36, 56, 81
We'll try to find the pattern between the consecutive numbers in the series by calculating the differences:
12 - 6 = 6
21 - 12 = 9
36 - 21 = 15
56 - 36 = 20
81 - 56 = 25
The differences between consecutive numbers are:
6, 9, 15, 20, 25
for following a logical pattern 6 and 9 should be 5 and 10
if first difference is 5 then second number = 6 + 5 = 11
and second difference is 10 then third number = 11 + 10 = 21 (true)
so 12 is wrong number .

Alternative method:

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