A bag contains 4 white and 5 black balls. A ball is drawn at random from the bag. Find the probability that the ball is drawn is white.

We know that,


Probability of occurrence of an event


By permutation and combination, total no.of ways to pick r objects from given n objects is nCr


Now, total no.of ways to pick a ball from 9 balls is 9c1 = 9


Our desired output is to pick a white ball. So, no.of ways to pick a white ball from 4 white balls (because the white ball can be picked from only white balls) is 4c1 = 4


Therefore, the probability of picking a white ball


Conclusion: Probability of picking a white ball from 4 white balls and 5 white balls is


1