An urn contains 9 red, 7 white, and 4 black balls. A ball is drawn at random. Find the probability that the ball is drawn is

white or black


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 20 balls is 20c1 = 20


Our desired output is to pick a white or red ball. So, no.of ways to pick a white or red ball from 16 balls(because there are a total of 16 balls which are either red or white) is 16c1 = 16


Therefore, the probability of picking a white or black ball



Conclusion: Probability of picking a white or black ball from 9 red, 7 white, and 4 black balls is


1