A coin is tossed three times. Given that at least one head appears, what is the probability that exactly two heads will appear?
3/7, Barron’s Math too? Lol.
@Frigidcold yep, can you please explain I don’t understand the explanation in the book.
Three coins have eight possible outcomes. I hope you can at least figure this out. 2 x 2 x 2.
Seven of these outcomes have at least 1 head, the only one without being TTT. Thus 7/8.
Three of these outcomes have at least 2 heads, HHT, HTH, and THH. Thus 3/8.
(3/8)/(7/8) = 3/7
If you know Bayes’ theorem, you can also apply it in a straightforward manner here.