Finding the minimum ratio out of many lines of input
I guess my comment really was an answer in a philosophical way.  So here is the answer:

Use names for your variables that have meaning.

There are lots of advantages to naming your variables well.  Many people have looked at this question only with a very abstract idea of what you are trying to do.  This makes it difficult to find improvements.  If people know exactly what you are trying to do then they can work out clever ways to achieve that.

As palacsint said: 'It won't be any slower if you use longer and readable variable names' but it may well be faster when people understand it and can see how to improve it.