All of the area were under a marginal risk (A) for

Find the missing term in the following question:

What number should replace the question mark? 

In the following question, a series is given with one term missing. Choose the correct alternative from the given ones that will complete the series.

Find the missing number.

Select the number from among the given option that can replace the question mark (?) in the following series.

6, 31, 126, 381, 766, ?

In the following question, select the missing number from the given alternatives.

45, 15, 60, 75, 135, ?

Study the given pattern carefully and select the number that can replace the question mark (?) in it.

First row: 14, 12, 108

Study the given matric carefully and select the number from among the given options that can replace the question mark (?) in it.

Select the number from among the given option that can replace the question mark (?) in the following series.

4, 21, 86, 261, 526, ?

Choose the correct alternative from the given ones that will complete the series.

3.5 , ?,  8.3, 10.7, 13.1 , 15.5