Select the number from the given options that can replace the question mark (?) in the following series.
21, 23, 20, 22, 19, 21,?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 18.
The series follows this pattern:
21 + 2 = 23, 23 - 3 = 20, 20 + 2 = 22, 22 - 3 = 19, 19 + 2 = 21, 21 - 3 = 18