Look at this series: 15, 15, 27, 27, 39, 39, 51, 51, ... What number should fill the blank? Choose the correct choice.
A) 51  B) 39  C) 63  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 63
<result>C</result>
Look at this series: 15, 15, 27, 27, 39, 39, 51, 51, ... What number should fill the blank?