Practice Problems for  the Lander Math Contest
Module 8, Problems (23-25)

23) From a jar with 8 fair coins and 2 unfair coins (the
probability of head in the
unfair coins is 90%, P(H)=.9), we
pick a coin at random and toss it 4 times. What is the
probability that there will be exactly 3 heads and one tail?

24) In previous problem, if the outcome of 4 tosses was
exactly 3 heads and one tail what is the probability that the
coin was unfair?

25) In problem 23) if the outcome of 4 tosses was exactly 2
heads and 2 tails what is the probability that the coin was fair
one?