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Find the WRONG number in the series: 4, 5, 12, 39, 155, 805

Competition practiceNumber Series

A39
B160
C155
D805

Step-by-Step Solution

Pattern is

\times 1 + 1, \times 2 + 2, \times 3 + 3, \times 4 + 4, \times 5 + 5

;

39 \times 4 + 4 = 160

, not 155. So 155 is wrong.

Answer: C) 155

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