What number should replace the question mark?

125, 138, 164, ?, 255

The given number series is 6, 8, 5, 10, 4, 14

6

6 + 2 = 8

8 - 3 = 5

5 + 5 = 10

10 - 7 = 3

3 + 11 = 14

...

Hence, the odd man in the given series is 4.

The given number series 100, 101, 97, 105, 90

100

100 + 1^2 = 101

101 - 2^2 = 97

97 + 3^2 = 106 ( not 105)

106 - 4^2 = 90

Hence, the odd man in the given series is 105.

The given number series is 180, 90, 60, 40, 36

It follows a pattern that,

180 x 1/2 = 90

90 x 2/3  = 60

60 x 3/4  = 45 (NOT 40)

45 x 4/5  = 36

Hence, the wrong number in the given series is 40.

The given number series is 3, 12, 39, 120, 364

$$\begin{gathered} 3 \\ 3 + 32 = 3 + 9 = 12 \\ 12 + 33 = 12 + 27 = 39 \\ 39 + 34 = 39 + 81 = 120 \\ 120 + 35 = 120 + 243 = 363 (Not 364) \end{gathered}$$

The given number series is 120, 36, 6, 2, 1, 1

120

120/5 = 24 (not 36)

24/4 = 6

6/3 = 2

2/2 = 1

1/1 = 1

Hence, the odd man in the given number series is 24.

The given series 24.3, 23.1, 20.7, 17.1, 12.4 follows a pattern that

24.3

24.3 - 1.2 = 23.1

23.1 - 2.4 = 20.7

20.7 - 3.6 = 17.1

17.1 - 4.8 = 12.3 not 12.4

Hence, the odd man or odd number in the given series is 12.4

Here in the given number series 49, 81, 121, 169, 196, 225

Except 196 all others are squares of odd numbers, whereas 196 is a square of 14 which is an even number.

Hence, the odd man in the given number series is 196.

The given number series 8, 18, 56, 232, 1165 

8

8 x 2 + 2 = 18

18 x 3 + 3 = 57 (not 56)

57 x 4 + 4 = 232

232 x 5 + 5 = 1165

Hence, the odd man in the given series is 56.