May 2018 Brain Puzzler Solution

Q: Two coins are flipped and you cannot see the outcome but are told that at least one is a head.  What is the probability that the other coin also landed on heads?
A: 1/3
This is a classic probability question.  Once you know that one coin is a head, there are 3 possible outcomes for the two coins with at least one head.
HH
HT
TH
Since you know that one is a heads, and there are 3 possible outcomes, the probability is 1/3.

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