EduGoog
In following questions, one term in number series is incorrect.

Find out the incorrect number 3, 7, 15, 39, 63, 127, 255, 511

Option:
A. 15
B. 39
C. 63
D. 127
Answer: B . 39

Justification:

Each number in the series is multiplied by 2 and the result increased by 1 to obtain the next number.
So, 39 is wrong and should be replaced bu (15 * 2 + 1)   i.e. 31.

Next