Look at this series: 15, __, 27, 27, 39, 39, ... What number should fill the blank?	Choose the most appropriate option:  A) 51  B) 39  C) 23  D) 15  E) None
Explanation: 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.   Answer: Option 15
<result>D</result>
Look at this series: 15, __, 27, 27, 39, 39, ... What number should fill the blank?