An urn consists of 20 red balls and 30 green balls. We choose 10 balls at random from the urn. The sampling is done without replacement (repetition not allowed).

a. What is the probability that there will be exactly 4 red balls among the chosen balls?

b. Given that there are at least 3 red balls among the chosen balls, what is the probability that there are exactly 4 red balls?

Guest Mar 7, 2020