I know of one way, but I'm not sure if this is what you're looking for. Let me give an example to help:
I have 2 cereal boxes. One that weighs 10oz and cost $5, and another that weighed 6oz and cost $2. To compare them, you'd create ratios. I'll do oz/$
&

Simplify. You should get 2 and 3. Now we know that the 10oz for $5 is a better deal than 6oz for $2.