A galvanometer coil has a resistance $90 \mathrm{\Omega }$ and full scale deflection current $10 \mathrm{mA}$. A $910 \mathrm{\Omega }$ resistance is connected in series with the galvanometer to make a voltmeter. If the least count of the voltmeter is $0.1 \mathrm{V}$, the number of divisions on its scale is $20x$, then find $x.$