The two-region Milne problem results of Ganapol and Pomraning are used in a proposed solution to an inverse transport problem in which there are two adjacent, optically-thick, isotropic-scattering layers. Equations are obtained for approximately estimating the mean number of secondaries of each region using only the normally-directed angular fluxes and the scalar fluxes and currents at the external boundaries. The impracticality of extending the analysis to two regions with anisotropic scattering or to more than two isotropic-scattering regions is discussed, as well as limitations of the proposed solutions.