Question

There are 5 brilliant students in class XI and 8 brilliant students in class XII. Each class has 50 students. The odds in favour of choosing the class XI are 2 : 3. If the class XI is not chosen then the class XII is chosen. A student is a chosen and is found to be brilliant, find the probability that the chosen student is from class XI.

Answer 1

Let E and F be the events ‘Class XI is chosen’ and ‘Class XII is chosen’ respectively. 

Then P(E) = 2/5, P(F) = 3/5

Let A be the event ‘Student chosen is brilliant’.