Current Electricity

Two resistance \(\mathrm{X}\) and \(\mathrm{Y}\) are connected in the two gaps of a meterbridge and the null points is obtained at \(20 \mathrm{~cm}\) from zero end. When the resistance of \(20 \Omega\) is connected in series with the smaller of the two resistance \(\mathrm{X}\) and \(\mathrm{Y}\), the null point shifts to \(40 \mathrm{~cm}\) from left end. The value of smaller resistance in ohm is