From the problem, we have 3.25% to convert into fraction.
Note that percentage a% can be written as a/100
So 3.25% will be :

From here, we can multiply the numerator and the denominator by 100 to make 3.25 a whole number.

Next step is to simplify the fraction by getting the factors of the numerator and the denominator.
325 = 25 x 13
10000 = 25 x 400
Rewriting it again :

Cancel the common factor (25)

The answer is 13/400