Which of the following numbers will replace the question mark (?) in the given series?
9, 17, 33, 65, ?, 257
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 129.
Given series: 9, 17, 33, 65, ?, 257
9 × 2 - 1 = 17; 17 × 2 - 1 = 33; 33 × 2 - 1 = 65; 65 × 2 - 1 = 129; 129 × 2 - 1 = 257