Aptitude - Odd Man Out and Series

Exercise :: Odd Man Out and Series - Missing No.

Insert the missing number.
6. 

11, 13, 17, 19, 23, 29, 31, 37, 41, (....)

A. 43
B. 47
C. 53
D. 51

Answer: Option A

Explanation:

Numbers are all primes. The next prime is 43.

7. 

8, 24, 12, 36, 18, 54, (....)

A. 27
B. 108
C. 68
D. 72

Answer: Option A

Explanation:

Numbers are alternatively multiplied by 3 and divided by 2.

So, the next number = 54 ÷ 2 = 27.


8. 

2, 6, 12, 20, 30, 42, 56, (....)

A. 61
B. 64
C. 72
D. 70

Answer: Option C

Explanation:

The pattern is 1 x 2, 2 x 3, 3 x 4, 4 x 5, 5 x 6, 6 x 7, 7 x 8.

So, the next number is 8 x 9 = 72.


9. 

4, -8, 16, -32, 64, (....)

A. 128
B. -128
C. 192
D. -192

Answer: Option B

Explanation:

Each number is the proceeding number multiplied by -2.

So, the required number is -128.


10. 

7, 26, 63, 124, 215, 342, (....)

A. 481
B. 511
C. 391
D. 421

Answer: Option B

Explanation:

Numbers are (23 - 1), (33 - 1), (43 - 1), (53 - 1), (63 - 1), (73 - 1) etc.

So, the next number is (83 - 1) = (512 - 1) = 511.