A new scheme is proposed for the simultaneous prediction of the modulus and yield (or tensile) strength of binary blends, which employs a two-parameter equivalent box model and the data on the continuity of constituents acquired from the percolation theory, Prediction of the elastic modulus in the linear stress-strain region assumes "perfect" interfacial adhesion; at yielding (or breaking), the upper and lower bounds have to be distinguished, those bounds being related, respectively, to the interfacial adhesion sufficient and insufficient for the transmission of the acting stress. The modulus and the upper bound of yield (or tensile) strength are monotonic functions of the blend composition within the interval delimited by the values characterizing the components. The lower bound of strengths passes through a minimum (close to the 50/50 composition) linked to the minimum sum of the continuity parameters of the constituents, Predicted dependences of the modulus and of the yield (or tensile) strength on the blend composition are ina good accord with experimental data selected from literature.