What will come at the place of question mark? 5, 9, 17, 33, 65, ?

Question

What will come at the place of question mark? 5, 9, 17, 33, 65, ?

1. A. 129 (Correct answer)
2. B. 120
3. C. 130
4. D. 127

Correct Answer

Option A — 129

Detailed Solution & Explanation

The correct answer is 129.

Key Points

• Look at the gaps: 5 → 9 (+4), 9 → 17 (+8), 17 → 33 (+16), 33 → 65 (+32).
• The difference doubles every step, so the next gap is +64, giving 65 + 64 = 129.
• Equivalently each term is (2 × previous) − 1: 2×65 − 1 = 129, confirming the answer two ways.
• When gaps double, the series usually hides a 2n±c formula — verifying with the second pattern catches arithmetic slips.