Sunday, 27 January 2013

27/01/2013 - Pool Balls (**)

This puzzle is rated 2-star (medium).


A cloth bag contains a single red pool ball. 

A second pool ball is chosen at random in such a way that it is equally likely to be a red or a yellow ball. The ball is added to the bag, the bag is shaken, and a ball is drawn at random. 

The withdrawn ball proves to be a red.


What is the probability that the ball remaining in the bag is also a red?

Check the solutions page for the correct answer.

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