Select the number from among the given options that can replace the question mark (?) in the following series.
11, 20, 37, 69, 131, ?, 489
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 251.
Given series: 11, 20, 37, 69, 131, ?, 489
11 × 2 - 2 = 20; 20 × 2 - 3 = 37; 37 × 2 - 5 = 69; 69 × 2 - 7 = 131; 131 × 2 - 11 = 251; 251 × 2 - 13 = 489