probability

Question

The probability that a student passes course A is .6. The probability that he passes course B is .3. The probability that he passes either A or B or both is .8. What is the probability that he passes both?

 

Answer 1

The Probability of (A or B) = P(A) + P(B) - P(A and B), solving for P(A and B) yields

 

P(A and B) = P(A) + P(B) - P(A or B) = .6 + .3 - .8 = .1

 

The probability that he passes both is 10%