I toss two coins and look at the outcome. I then tell you that at least one of the coins is showing up as "tails". What is the chance that the other one is showing "tails" as well?

(from techInterview.org)

Wake up, little boy. It doesn't matter what the other coins flipped to. A coin has only two sides. It only be either heads or tails. There is a 50% chance of it being tails. The only possible way it could have a 1/3 chance of being tails if if the coin is THREE-SIDED and two of them are heads. You absolutely cannot base the previous flips on whether a coin lands heads or tails.

Posted by Mike on 2002-05-10 16:03:04