Look at this series: 2, 4, 6, 8, 10, ... What number should come next?

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

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

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

Which of the following numbers will replace the question mark (?) in the given series?
111, 114, 119, ?, 135

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

Select the number from among the given options that can replace the question mark (?) in the following series.
121, 144, 169, 196, ?

What should come in place of the question mark (?) in the given series?
61 66 72 77 83 ?

What should come in place of the question mark (?) in the given series?
76 81 91 111 151 ?

What should come in place of the question mark (?) in the given series?
5, 11, 23, 47, 95, ?