NCERT Example 20 - Probability
Question: A doctor visits by train, bus, scooter or other means with probabilities 3/10, 1/5, 1/10, 2/5. Probabilities of being late are 1/4, 1/3, 1/12, 0 respectively. When he arrives late, find the probability that he came by train.
Answer: 1/2.
Full step-by-step NCERT solution with diagrams on Something by Zero.