6, 14.5, 31.5, 65.5, ?

What will come in the place of the question mark in the following series?

6, 14.5, 31.5, 65.5, ?

a) 133.5

b) 138.5

c) 135.5

d) 130.5

e) 136.5

Sol:

Logic in the series:

6 * 2 + 2.5 = 14.5

14.5 * 2 + 2.5 = 31.5

31.5 * 2 + 2.5 = 65.5

65.5 * 2 + 2.5 = 133.5

So, missing term in the series = 133.5