an experiment consists of tossing 4 fair (not weighted) coins, except one of the 4 coins has a head on both sides. Compute the probability of obtaining exactly 3 heads.

Question

an experiment consists of tossing 4 fair (not weighted) coins, except one of the 4 coins has a head on both sides. Compute the probability of obtaining exactly 3 heads.

Answer 1

If one of the coins has heads on both sides, the problem reduces to the probability of obtaining two heads in three tosses. This is C(3,2) * (1/2)³ = 3/8.