Brain Teasers
Two Coins
Probability
Probability puzzles require you to weigh all the possibilities and pick the most likely outcome.Probability
Suppose I flip two coins without letting you see the outcome, and I tell you that at least one of the coins came up heads. What is the probability that the other coin is also heads?
Hint
You might initially think that the answer is 1/2, but it is not so.Answer
1/3.For two coins, there are four possible outcomes: HH, HT, TH, and TT. Since we know that at least one was a head, we can eliminate TT. Of the remaining three possibilities, only 1 allows the second head: HH.
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