Count the number of decimal places.
Put the non-leading-zero portion of the number over "1", followed by the same number of zeroes as there were decimal places.
Simplify, as necessary.
For instance:
. . . . .0.25 = 25/100 = 1/4
. . . . .0.05 = 5/100 = 1/20
. . . . .2.5 = 25/10 = 5/2 = 2<sup>1</sup>/<sub>2</sub>
And so forth.
Eliz.