Number Series - Verbal and Reasoning

Directions to SolveLook carefully for the pattern, and then choose which pair of numbers comes next.
Q1:

Look at this series: 15, __, 27, 27, 39, 39, ... What number should fill the blank?

A 51

B 39

C 23

D 15

ANS:D - 15

In this simple addition with repetition series, each number in the series repeats itself, and then increases by 12 to arrive at the next number.