Which number will replace the question mark (?) in the following series?
12, 25, 51, 103, ?, 415, 831

The missing number in the series 28, 33, 31 ?, 34,39 is

In the sequence 20, 10, 10, 15, 30, 75, X, find the value of X.

Find the next number in the series:
9,20,38, 65, ?

In the following question, select the missing number from the given series :
13, 35, 73, 215, 433, ?

Find the missing value '?'
4, 23, 60, 121,  ?

Find the missing terms in the following series:
2, 15, 4, 12, 6, 7, ?, ?

A series is given with one term missing. Select the correct alternative from the given ones that will complete the series.
-36, -68, -132, -260, ?, -1028, -2052, -4100

What will come in place of the question mark (?) in the given series?
103 119 135 151 167?

What should come in place of the question mark (?) in the given series?
26 26 38 38 50 50 ?