JEE Main 2024 Mathematics question
There are three bags X, Y and Z. Bag X contains 5 one-rupee coins and 4 five-rupee coins; Bag Y contains 4 one-rupee coins and 5 five-rupee coins and Bag Z contains 3 one-rupee coins and 6 five-rupee coins. A bag is selected at random and a coin drawn from it at random is found to be a one-rupee coin. Then the probability, that it came from bag Y, is:
Answer: (A)
Solution
Bayes: (4/9)/((5 + 4 + 3)/9) = 4/12 = 1/3.