The probabilities that he will be late are 1 1
, , and1
4 3
12,
if he comes by train, bus and scooter respectively, but if he comes by other means of
transport, then he will not be late When he arrives, he is late What is the probability
that he comes by train Solution Let E be the event that the doctor visits the patient late and let T1, T2, T3, T4
be the events  that the doctor comes by train, bus, scooter, and other means of transport
respectively