Answer:

Expression for root mean square velocity is as follows:

$ {{v}_{rms}}=\sqrt{\frac{v_{1}^{2}+v_{2}^{2}+v_{3}^{2}+……+v_{n}^{2}}{n}} $

For two meolecules, the formula reduces to:

$ {{v}_{rms}}=\sqrt{\frac{v_{1}^{2}+v_{2}^{2}}{n}} $

$ {{v}_{1}}=9\times {{10}^{6}}m/s,{{v}_{2}}=1\times {{10}^{6}}m/s $

$ {{v}_{rms}}=\sqrt{\frac{{{(9\times {{10}^{6}})}^{2}}+{{(1\times {{10}^{6}})}^{2}}}{2}}={{10}^{6}}\sqrt{\frac{81+1}{2}} $

$ {{v}_{rms}}=\sqrt{41}\times {{10}^{6}}m/s $