$\left\{ \begin{matrix}{{p}_{1}}=\frac{{{V}^{2}}}{{{R}_{1}}}  \\{{p}_{2}}=\frac{{{V}^{2}}}{{{R}_{{}}}}  \\\end{matrix} \right.\Rightarrow \frac{{{R}_{1}}}{{{R}_{2}}}=\frac{{{p}_{2}}}{{{p}_{1}}}=\frac{500}{200}=2/5$