An urn contains 5 black and 20 white marbles. They are to be drawn one at a time until all of one color has been exhausted.

What is the probability that the color of the first draw correctly predicts the first color exhausted?

(In reply to re(3): solution by Ady TZIDON)

I have added a prefatory paragraph to state that "last marble" in my description refers to what would be the last marble had the procedure continued until no more marbles are left, this color being the opposite of the first color to be exhausted.

Posted by Charlie on 2015-08-12 14:46:30