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?
There are 3 possibilities with at least one tail (HT, TH, TT). Only one has both tails. Therefore, the probability is 1/3.
Posted by Math Man
on 2013-01-05 13:54:19