Solution (source code)

= Solution

The <Maxwell speed distribution> is proportional to $v^2e^{-mv^2/(2k_BT)}$. Setting its logarithmic derivative to zero gives the most probable <speed>:
$$
\boxed{v_{\rm mp}=\sqrt{\frac{2k_BT}{m}}=\sqrt{\frac{2RT}{M}}
\simeq3.95\times10^2\,\mathrm{m\,s^{-1}}.}
$$
Use molecular <oxygen>, with $M\simeq0.032\,\mathrm{kg\,mol^{-1}}$, and $T=300\,\mathrm K$.