From the Exploring Data website - http://curriculum.qed.qld.gov.au/kla/eda/
© Education Queensland, 1997

Monty Hall Puzzle Solution

You have tried to solve the puzzle before looking at this page, haven't you? :-)

The answer is that you should always switch. If you do so, the probability of winning is 2/3. If you don't switch the probability of winning is 1/3.

If you disagree with this answer, you may wish to think about the puzzle a bit more, before moving on the the explanations.