So five molecules altogether. So I add up to five molecules p blue one plus p blue two plus p red one plus p red two plus p red three. Now, I could also say that my p total is equal to the pressure due to blue gas molecules. This guy plus this guy plus the pressure due to red gas molecule or p one plus p two plus p three. Another way of saying this is the pressure due to my blue gas molecule is the partial pressure of my blue molecule and this guy is the partial pressure of my red molecule. So partial pressure refers to the pressure exerted by one type of gas molecule.