[" The radii of two planets are respectively "],[R_(1)" and "R_(2)" and their densities are "],[" respectively "rho_(t)" and "rho_(2)" .The ratio of the "],[" accelerations due to gravity at their "],[" surfaces is "],[[(1)g_(1):g_(2)=R_(1)R_(2),:R_(2)rho_(2)],[(3)g_(1):,g_(2)=R_(1)rho_(1):R_(2)rho_(2)],[(4)g_(1):g_(2)=R_(1)rho_(1):,R_(2)rho_(2)]]