2.5, 3.5, 9, 40, ?

Find the next number in the above-given series?

The given number series is 8, 16, 20, 36, 68

8

8 x 2 - 4 = 12 (NOT 16)

12 x 2 - 4 = 20

20 x 2 - 4 = 36

36 x 2 - 4 = 68

Hence, the odd man in the given series is 16.

The given series is 8, 14, 24, 60, 180

8

8 x 1.5 = 12 (NOT 14)

12 x 2 = 24

24 x 2.5 = 60

60 x 3 = 180

Hence, the odd man in the given series is 12.

The given series is 1 6 27 124 650

1

1 + 2 x 2 = 6

6 + 3 x 3 = 27

27 + 4 x 4 = 124

124 + 5 x 5 = 645 (NOT 650)

Hence, the odd man in the given number series is 650.

The given series is 1000, 1012, 988, 1024, 978

1000

1000 + 12 = 1012

1012 - 24 = 988

988 + 36 = 1024

1024 - 48 = 976 (Not 978)

The given series is 15, 19, 27, 38, 55, 75

15

15 + 4 = 19

19 + 8 = 27

27 + 12 = 39

39 + 16 = 55

55 + 20 = 75

Hence, the odd number in the given series is 38.

The given number series is 5, 8, 40, 90, 664

5

5 - 1 x 2 = 8

8 - 3 x 4 = 20 (NOT 40)

20 - 5 x 6 = 90

90 - 7 x 8 = 664

The given number series is 152, 124, 96, 69, 40

152

152 - 28 = 124

124 - 28 = 96

96 - 28 = 68 (not 69)

68 - 28 = 40

Hence, the odd man in the given number series is 69.

The given number series is 3, 11, 80, 291, 803

$$\begin{gathered} 3 \\ 3 + 23 = 3 + 8 = 11 \\ 11 + 43 = 11 + 64 = 75 (not 80) \\ 75 + 63 = 75 + 216 = 291 \\ 291 + 83 = 291 + 512 = 803 \end{gathered}$$