Famous Probability Interview Problem
James Horner is having two coins in his hand. Out of the two coins, one is a real coin and the second one is a faulty one with Tales on both sides. He blind folds himself choose a random coin and tosses it in the air. The coin falls down with Tale facing upwards. What is the probability that this is the faulty coin?




While tossing the coins in this case only two cases are favorable:

1) A1 (H) A2 (H)

2) A2 (H) A1 (H)

3) B1 (H) B2 (T)

4) B2 (T) B1 (H)

Since the fourth case is not feasible, the probability is 2/3.