The average multiplicity in hadron-nuclear interactions at high energies was calculated in assumption of a number of successive inelastic collisions of the formed leading system with the nuclear nucleons. When describing elementary acts the model of two mechanisms was used which allows one to take into account naturally the space-time pattern of interaction in the nucleus. The model describes the experimental data and allows one to investigate the distribution of the elasticity coefficient in hadron-nucleon collisions. 11 refs.; 2 figs.; 4 tabs.