Question

A bag contains (2n + 1) coins. It is known that n of these coins has a head on both sides whereas the rest of the coins are fair. A coin is picked up at random from the bag and is tossed. If the probability that the toss results in a head is 31/42, determine the value of n. Select the correct answer from above options

Answer 1

Given, n coins are two headed coins and the remaining (n + 1) coins are fair. Let E1: the event that unfair coin is selected E2: the event that the fair coin is selected E: the event that the toss results in a head So, P(E1) = n/(2n + 1) and P(E2) = (n + 1)/ (2n +1) P(E/E1) = 1 (As it’s a sure event) P(E/E2) = ½ Therefore, the required value of n is 10.