Reference: toFraction
toFraction is used to obtain the numerator p and denominator q of a rational number (or approximated real number) x = p/q (or at least very close to). toFraction(x) returns the real number x as a string of the form "p/q" where p and q are integers, and so that the rational number p/q ≈ x. For instance, toFraction(0.0843373493976) = "7/83".