Give a quick stream of consciousness before answering the following question. In each series, look for the degree and direction of change between the numbers. In other words, do the numbers increase or decrease, and by how much? Look at this series: 5, 43, 15, 33, 25, ...What number should come next?
Options:
(A) 10
(B) 40
(C) 23
(D) 13
(E) 20
C
23
This is an alternating addition and subtraction series. In the first pattern, 10 is added to each number to arrive at the next. In the second, 10 is subtracted from each number to arrive at the next.
The answer: (C).