What will come in place of the question mark (?) in the following number series? 1, 3, 7, 15, ? MCQ with Answer and Explanation

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What will come in place of the question mark (?) in the following number series? 1, 3, 7, 15, ?

A. 30

B. 35

C. 32

D. 31

Answer: Option D

Solution (By JKSSB Mock Tests)

Each term is obtained by multiplying the previous term by 2 and adding 1. (1×2)+1=3, (3×2)+1=7, (7×2)+1=15. The next term is (15×2)+1=31.

This question belongs to: Reasoning Number Series

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Question #1

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What will come in place of the question mark (?) in the following number series? 1, 8, 27, 64, 125, ?

A. 216

B. 196

C. 144

D. 169

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Correct Answer: Option A

Explanation:
The series consists of cubes of consecutive integers: 1³, 2³, 3³, 4³, 5³. The next term is 6³=216.

This question belongs to: Reasoning Number Series

Question #2

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What will come in place of the question mark (?) in the following number series? 5, 15, 45, 135, ?

A. 360

B. 270

C. 540

D. 405

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Correct Answer: Option D

Explanation:
Each term is multiplied by 3. Therefore, 135×3=405.

This question belongs to: Reasoning Number Series

Question #3

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What will come in place of the question mark (?) in the following number series? 7, 10, 15, 22, 31, ?

A. 42

B. 38

C. 40

D. 44

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Correct Answer: Option A

Explanation:
The differences are: 3, 5, 7, 9. These are consecutive odd numbers. The next difference is 11. Therefore, 31+11=42.

This question belongs to: Reasoning Number Series

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