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
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.
Math Confidence by Robin the Math Lady 