Direct & Inverse Variation: Two Variables
These two types of problems always involve two letters (usually x and y) and usually start the same way: if the problem has the words "varies directly" in it (or says two things are "proportional"), you just write down "y=kx" and start plug-and-chugging. If the problem says "varies inversely" (or variables are "inversely proportional"), you write down y=k/x and start plug-and-chugging. Sound too easy? What can I say: the same four steps will get you through every one of these things.