A voltmeter of variable ranges $3 \mathrm{V},\mathrm{ }15 \mathrm{V},\mathrm{ }150 \mathrm{V}$ is to be designed by connecting resistances ${\mathrm{R}}_1,\mathrm{ }{\mathrm{R}}_2,\mathrm{ }{\mathrm{R}}_3$ in series with a galvanometer of resistance $\mathrm{G}\mathrm{ }=\mathrm{ }20 \mathrm{\Omega }$, as shown in the figure. The galvanometer gives full pass through its coil. Then, the resistances ${\mathrm{R}}_1,\mathrm{ }{\mathrm{R}}_2$ and ${\mathrm{R}}_3$ (in kilo ohms) should be, respectively