So average kinetic energy is equal to one half times and times VR mass squared equals one half times mass. Now, I take my formula for BRMs, for Dances, and plug into my equation. The radical will disappear, because the radical has an exponent of a half a half times two is one. So I simply get one half times mass over molam mass times R and T. Now, remember, molar mass has units of mass divided by moles. So the mass will cancel, and moles will go on top, and we'll get one half the mass will cancel. So this M and this M will cancel.