Select the number from among the given options that can replace the question mark (?) in the following series.
3, 6, 9, 18, 21, ?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 42.
Give series: 3, 6, 9, 18, 21, ?
3 × 2 = 6; 6 + 3 = 9; 9 × 2 = 18; 18 + 3 = 21; 21 × 2 = 42