A gambler is holding three coins.
One coin is an ordinary quarter, the second has two heads, the third has two tails.
The gambler randomly chooses one of the coins and flips it, the coin shows head.
What is the chance that the other side shows tail?
The chance that the other is tail is one over three (1/3) as only one coin (the ordinary coin) in the three coins has head on one side and tail on the other side.
The gambler’s first toss shows heads. The question was to find the probability that the other side of the coin will show tail and not to find the probability of tails coming up. 😛
Answer is: One third.