1992 AIME Problem 5

Let S be the set of all rational numbers r, 0<r<1, that have a repeating decimal expansion of the form

0 . a b c a b c a b c \ldots=0 . \overline{a b c}

where the digits a, b, c are not necessarily distinct. To write the elements of S as fractions in lowest terms, how many different numerators are required?