What will come in place of the question mark (?) in the following number series? 9, 17, 33, 65, ? MCQ with Answer and Explanation

What will come in place of the question mark (?) in the following number series? 9, 17, 33, 65, ?
A. 129
B. 121
C. 125
D. 123
Answer: Option A
Solution (By JKSSB Mock Tests)
Each term is obtained by multiplying by 2 and subtracting 1. (9×2)-1=17, (17×2)-1=33, (33×2)-1=65. The next term is (65×2)-1=129.

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Practice More Number Series Questions

Question #1
What will come in place of the question mark (?) in the following number series? 12, 18, 26, 36, ?
A. 44
B. 48
C. 50
D. 46

Correct Answer: Option B


Explanation:
The differences are: 6, 8, 10. These are increasing by 2. The next difference is 12. Therefore, 36+12=48.

This question belongs to: Reasoning Number Series
Question #2
What will come in place of the question mark (?) in the following number series? 4, 8, 12, 20, ?
A. 28
B. 36
C. 24
D. 32

Correct Answer: Option D


Explanation:
The pattern alternates: +4, ×2? No, 4+4=8, 8+4=12, 12+8=20. Actually, it's adding consecutive even numbers: +4, +4, +8. But more precisely: 4+4=8, 8+4=12, 12+8=20, 20+12=32? Let's re-evaluate: The differences are 4, 4, 8, 12. Not a clear pattern. A better pattern: each term is the sum of the previous two terms? 4+8=12, 8+12=20, 12+20=32. Yes, this is a Fibonacci-like series. The next term is 12+20=32.

This question belongs to: Reasoning Number Series
Question #3
What will come in place of the question mark (?) in the following number series? 5, 12, 26, 54, ?
A. 112
B. 114
C. 110
D. 108

Correct Answer: Option C


Explanation:
Each term is obtained by multiplying by 2 and adding 2. (5×2)+2=12, (12×2)+2=26, (26×2)+2=54. The next term is (54×2)+2=110.

This question belongs to: Reasoning Number Series