11. 0, 3, 8, 15, 24, 35, 48, 63, ...

- Option : A
- Explanation : The series is 1
^{2}− 1, 2^{2}− 1, 3^{2}− 1 and so on. The next number is 9^{2}− 1 = 80.**Alternative solution**: The differences between the numbers across the series are 3, 5, 7, 9, 11, 13, 15 and 17. The next number is 63 + 17 = 80.

12. 2, 5, 10, 17, 26, 37, ..., 65

- Option : A
- Explanation : The series is 1
^{2}+ 1, 2^{2}+ 1, 3^{2}+ 1 and so on. The next number is 7^{2}+ 1 = 50.

14. 1, 8, 27, 64, 125, 216, ...

- Option : B
- Explanation : The series is 1
^{3}, 2^{3}, 3^{3}, etc. The missing number is 7^{3}= 343.

15. 2, 9, 28, 65, 126, 217, 344, ...

- Option : A
- Explanation : The series is 1
^{3}+ 1, 2^{3}+ 1, 3^{3}+ 1 and so on. Thus, the missing number is 8^{3}+ 1 = 513.

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