There are three boxes, each with two drawers.
Box I has a gold coin in each drawer
Box II has a silver coin in each drawer
Box III has a gold coin in one drawer and a silver coin in the other.
One box is chosen at random and a drawer is opened from that box. If it contains a gold coin, find the probability that it is in Box I.
Solution. Denote the events that Box I, Box II and Box III are chosen by A, B and C, respectively. Then we know that ...
Probabilities based on random selection are calculated. Some knowledge of probability theory may be required to understand the solution.