# Example 20 - Chapter 13 Class 12 Probability

Last updated at Feb. 15, 2020 by Teachoo

Last updated at Feb. 15, 2020 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 3/10 , 1/5 , 1/10 and 2/5 . The probabilities that he will be late are 1/4 , 1/3 and 1/12 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?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) =(๐(๐1) ร ๐(๐ฟ|๐1))/(๐(๐1) ร ๐(๐ฟ|๐1) + ๐(๐2) ร ๐(๐ฟ|๐2) + ๐(๐3) ร ๐(๐ฟ|๐3) + ๐(๐4) ร ๐(๐ฟ|๐4)) P(T1) = Probability that doctor comes by train = ๐/๐๐ P(L|T1) = Probability that doctor comes late if he comes by train = ๐/๐ P(T2) = Probability that doctor comes by bus = ๐/๐ P(L|T2) = Probability that doctor comes late if he comes by bus = ๐/๐ P(T3) = Probability that doctor comes by scooter = ๐/๐๐ P(L|T3) = Probability that doctor comes late if he comes by scooter = ๐/๐๐ P(T4) = Probability that doctor comes by other means of transport = ๐/๐ P(L|T4) = Probability that doctor comes late if he comes by other means of transport = ๐ Putting values in formula, P(T1|L) =(๐(๐1) ร ๐(๐ฟ|๐1))/(๐(๐1) ร ๐(๐ฟ|๐1) + ๐(๐1) ร ๐(๐ฟ|๐1) + ๐(๐1) ร ๐(๐ฟ|๐1) + ๐(๐1) ร ๐(๐ฟ|๐1)) = (3/(10 ) ร 1/4)/( 3/(10 ) ร 1/4 + 1/(5 ) ร 1/3 + 1/(10 ) ร 1/12 + 2/(5 ) ร 0 ) =(3/( 40 ) )/( 18/(120 ) ) = 3/40ร120/18 =360/720 = ๐/๐

Examples

Example 1

Example 2

Example 3

Example 4

Example 5 Important

Example 6

Example 7 Important

Example 8

Example 9 Important

Example 10

Example 11 Important

Example 12 Important

Example 13 Important

Example 14 Important

Example 15 Important

Example 16

Example 17 Important

Example 18 Important

Example 19 Important

Example 20 Important You are here

Example 21 Important

Example 22

Example 23

Example 24 Important

Example 25 Important

Example 26 Important

Example 27 Deleted for CBSE Board 2021 Exams only

Example 28 Important Deleted for CBSE Board 2021 Exams only

Example 29 Important Deleted for CBSE Board 2021 Exams only

Example 30 Important Deleted for CBSE Board 2021 Exams only

Example 31 Important Deleted for CBSE Board 2021 Exams only

Example 32 Important Deleted for CBSE Board 2021 Exams only

Example 33 Important

Example 34 Important Deleted for CBSE Board 2021 Exams only

Example 35 Important

Example 36 Important

Example 37 Important

Chapter 13 Class 12 Probability

Serial order wise

About the Author

Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 10 years. He provides courses for Maths and Science at Teachoo.