[probability theory] simple question about conditional probability

[rahl___]

Hi all,

I've got this very simple problem:

We have K red balls [or what is the most popular item in combinatorics] and L black balls. If we take one red ball and one black ball and then randomly pick one of them, the probability of getting the red one equils p. We mix all of them, so now we have K+L balls and pick one at random. what is the probability, that it is the red one?

I know it is an elementary problem, but I never really got into that bayes' theorem, which I need to use here, right? I would be grateful for simple and plain explanation.

thanks for your time,
rahl.

 

[whome9]

Venn diagrams are a way easy method for visualizing Bayes' equations.