Continuous kinetics is applied to study the simultaneous occurrence of polymerization and degradation in polydisperse systems. The rate constants of all reactions are assumed to be independent of the molar masses of the species reacting. For an arbitrarily chosen initial distribution the continuous rate equation is approximately solved, by assuming a Schulz-Flory distribution with time-dependent parameters to be valid during the whole reaction time. The temporal change of the continuous distribution and of its moments is predicted. After infinite time the composition of the polydisperse system is exactly described by a Schulz-Flory distribution with the non-uniformity U=1. Presuming a monomeric initial condition many years ago Blatz and Tobolski found the exact discontinuous distribution. The comparison of the approximation method developed and of the exact results by Blatz and Tobolski yields an excellent accordance.