Fill in the blank with the correct number in this number series: 5, 15, 7, 12, __, 9, 11,... ?
Options:
(A) 6
(B) 9
(C) 8
(D) 7
(E) 5 OK. Let's think. Some random thoughts first:
In this simple alternating subtraction and addition series; The first series begins with 5 and adds 2; the second begins with 15 and subtracts 3, and so on. The answer: (B).