A mixture of 2 moles of helium gas (atomic mass $=4 \mathrm{u}$ ), and 1 mole of argon gas (atomic mass $=40 \mathrm{u}$ ) is kept at 300 K in a container. The ratio of their rms speeds $\left[\frac{\mathrm{V}_{\mathrm{rms}}(\text { helium })}{\mathrm{V}_{\mathrm{rms}}(\text { arg on })}\right]$, is close to