A $250$ $V$ $dc$ shunt machine has armature circuit resistance of $0.6$ $Ω$ and field circuit resistance of $125$ $Ω$. The machine is connected to $250$ $V$ supply mains. The motor is operated as a generator and then as a motor separately. The line current of the machine in both the cases is $50$ $A$. The ratio of the speed as a generator to the speed as a motor is ____________.