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

not 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 ⁿC_r

Now, total no.of ways to pick a ball from 20 balls is ²⁰c₁ = 20

Our desired output is to pick a black or red ball(not white). So, no.of ways to pick a black or red ball from 13 balls (because there are a total of 13 balls which are either red or black) is ¹³c₁ = 13

Therefore, the probability of not picking a white ball

Conclusion: Probability of not picking a white ball from 9 red, 7 white, and 4 black balls is