birbhadra let's do it without lumping the rho.. if the equation R=ρL/A………..implies R is propotional to length,...(where rho is taken as the constant at a given temperature)... does R=ρ/Pi*n2*L not imply ...R is inversely to L?... cause Rho, Pi and n are constant.......... same assumption is made in the two equations that rho is a constant.......