first divide 3/20 and you get 0.15, next just look at the ranges

a) 0 through 0.15
b) 0.15 through 0.2
c) 0.2 through 0.25
d) 0.25 through 0.3
e) 0.3 through .5

E has the largest range with it being 0.2. The problem you may have had is that you weren't instantly able to convert the fractions to decimals. One thing I did was made flashcards with the common fractions (according to my Barrons book) the only one that wasn't in Barrons was the 3/20, so that's the only one I had to figure out.

*edited to correct typo in d