If two coins are tossed simultaneously, what is the probability of getting exactly two heads? From a well-shuffled deck of 52 cards, what is the probability of getting a king? In a bag, there are 5 red balls and 7 black balls. What is the probability of getting a black ball?

Three bags contain 3 red, 7 black; 8 red, 2 black, and 4 red & 6 black balls respectively. 1 of the bags is selected at random and a ball is drawn from it. If the ball drawn is red, find the probability that it is drawn from the third bag. Sol: Let E1, E2, E3 and A are the events defined as follows. E1 = First bag is chosen E2 = Second bag is chosen E3 = Third bag is chosen A = Ball drawn is red Since there are three bags and one of the bags is chosen at random, so P (E1) = P(E2) = P(E3) = 1 / 3 If E1 has already occurred, then first bag has been chosen which contains 3 red and 7 black balls. The probability of drawing 1 red ball from it is 3/10. So, P (A/E₁) = 3/10, similarly P(A/E₂) = 8/10, and P(A/E₃) = 4/10. We are required to find P(E₃/A) i.e. given that the ball drawn is red, what is the probability that the ball is drawn from the third bag by Baye's rule