The Total solution for NCERT class 6-12
Let E1┬аbethe event that the student knows the answer, E2┬аbe the eventthat the student guess the answer and A be the event that the answer iscorrect.
Then┬аP (E1)= ┬╛
And┬аP (E2)= ┬╝
Also P (A|E1)= P (correct answer given that he knows) = 1
And P (A|E2)= P (correct answer given that he guesses)┬а= ┬╝
Now the probabilitythat he knows the answer, being given that answer is correct, is P (E1|A).
By using BayesтАЩtheorem, we have: