How do I compare a different objects with three rates? For instance, if I were to compare the price of apartments I would look at the price per square foot, a rate with two factors. But if I wanted to add a third value, let's say distance from town, which would increase gas consumption by a certain amount, how would I go about this?

For the two factor situation, I would divide the monthly cost of the apartment by the square footage and rank them. To add the third factor, would I divide the rate by the distance from town? Could a rate have more than two variables?