Practice Problem
Practice Problem > Logical Reasoning > Series

A series is given, with one term missing. Choose the correct alternative from the given ones that will complete the series.

4, 9, 19, 39, ?

Solution:

2nd term    =    2 × 1st term + 1 = 2 × 4 + 1 = 9
3rd term    =    2 × 2nd term + 1 = 19
4th term    =    2 × 19 + 1 = 39
5th term    =    2 × 39 + 1 = 79

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