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SNOOTCHIEBOOCHEE
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Homework Statement
A biased coin lands heads with probabilty 2/3. The coin is tossed 3 times
a) Given that there was at least one head in the three tosses, what is the probability that there were at least two heads?
b) use your answer in a) to find the probability that there was exactly one head, give that there was at least one head in the three tosses.
The Attempt at a Solution
a) So i figured the best way to do this would be to find the probability of the complement events and subtract one.
So i calculated P(No heads)+ P(exactly one head)= 1/27 + 6/27 = 7/27. So my answer would be 20/27. Which isn't the answer in the back of the book.
I assume i am wrong and i think it has to do with the following clause: "Given that there was at least one head in the three tosses"
Dunno how to factor that into my work... any help appreciated