In this article we examine three approaches, leading to different conclusions, for answering the question "Does the addition of inert gases at constant volume and temperature modify the state of equilibrium?" In the first approach, the answer is yes as a result of a common students' alternative conception; the second approach, valid only for ideal mixtures of gases, leads to a negative response, and in the third approach the answer is "a little" obtained from a more universal explanation. This last approach, ignored even in advanced chemistry textbooks, is valid for real mixtures of gases and the effects start to become verifiable at moderate pressures. Le Chatelier's principle application to pressure variations is explored in the context of the results from the different approaches. (Contains 3 tables.)