V}_{rms}}=\SQRT{\frac{3RT}{M}}\] i.e., \[\frac{{{V}_{1}}}{{{V}_{2}}}=\sqrt{\frac{{{T}_{1}}}{{{T}_{2}}}}\] \[\frac{5\times {{10}^{4}}}{10\times {{10}^{4}}}=\frac{1}{2}=\sqrt{\frac{{{T}_{1}}}{{{T}_{2}}}}\] \[\therefore {{T}_{2}}=4{{T}_{1}}\]