Utilize the formula pV=nRT This is the ideal gas law which is what boyles, law Charles law, and gay Lussac's laws are based off of. To use this formula, we must keep one variable constant in order to study the relationship between the other two. So what we must do is, say pressure and temperature are constant. The formula becomes V = nR But we must also consider what this means: from my understanding, R = the gas constant which drops out of our equation, so V = n. I feel that this shows us that the volume = number of moles of gas. If I am correct.