# Example 20 - Chapter 13 Class 12 Probability

Last updated at May 29, 2018 by Teachoo

Last updated at May 29, 2018 by Teachoo

Transcript

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 310 , 15 , 110 and 25 . The probabilities that he will be late are 14 , 13 and 112 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? Let T1 : Event that doctor came by Train T2 : Event that doctor came by Bus T3 : Event that doctor came by Scooter T4 : Event that doctor came by other means of transport L : Event that doctor arrives late We need to find out Probability of doctor comes by train if he is late i.e. P(T1|L) = 𝑃 𝑇1 × 𝑃(𝐿|𝑇1)𝑃 𝑇1 × 𝑃 𝐿|𝑇1 + 𝑃 𝑇1 × 𝑃 𝐿|𝑇1 + 𝑃 𝑇1 × 𝑃 𝐿|𝑇1 + 𝑃 𝑇1 × 𝑃(𝐿|𝑇1) Putting values in formula, P(T1|L) = 𝑃 𝑇1 × 𝑃(𝐿|𝑇1)𝑃 𝑇1 × 𝑃 𝐿|𝑇1 + 𝑃 𝑇1 × 𝑃 𝐿|𝑇1 + 𝑃 𝑇1 × 𝑃 𝐿|𝑇1 + 𝑃 𝑇1 × 𝑃(𝐿|𝑇1) = 310 × 14 310 × 14 + 15 × 13 + 110 × 112 + 25 × 0 = 3 40 1820 = 340 × 12018 = 360720 = 𝟏𝟐

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Example 20 Important You are here

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Chapter 13 Class 12 Probability

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About the Author

Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 8 years. He provides courses for Maths and Science at Teachoo. You can check his NCERT Solutions from Class 6 to 12.