Look at this series: 21, 9, 21, 11, 21, 13, 21, ... What number should come next?
Options
A. 14
B. 15
C. 21
D. 23
Correct Answer
15
Explanation
In this alternating repetition series, the random number 21 is interpolated every other number into an otherwise simple addition series that increases by 2, beginning with the number 9.
Number Series problems
Search Results
1. Look at this series: 53, 53, 40, 40, 27, 27, ... What number should come next?
This is a simple addition series with a random number, 8, interpolated as every other number. In the series, 6 is added to each number except 8, to arrive at the next number.
9. Look at this series: 31, 29, 24, 22, 17, ... What number should come next?