0140
28
0 0345
69
=
Example 20 A doctor is to visit a patient From the past experience, it is known that
the probabilities that he will come by train, bus, scooter or by other means of transport
are respectively 3 1 1
2
, ,
10 5 10and
5 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