Class 12 Maths Probability | Conditional Probability Problems |

**Conditional Probability Problems**:

**Example**: In a survey in a class it was found that the probability of a student watching Examfear videos is 0.8. and the probability that a student is both topper and also watches Examfear videos is 0.792. what is the probability that a student is a topper if he watches Examfear videos?

**Solution**:

Let E denotes the event that a person watches Examfear videos

Let F denotes the event that a person is topper . Then,

P(E) =The probability that a person watches Examfear videos =0.8

P(E∩F)=probability that one is both topper and also watches Examfear videos = 0.792

and P(F|E)= the probability that a person is a topper if he watches Examfear

videos=?

then according to Formula for conditional probability

P(F|E) = P(F∩E)/ P(E)

= 0.792/0.8

= 0.99

∴ The probability that a person is a topper if he watches Examfear videos is

0.99

.