Question

A bag contains 9 red marbles, 4 blue marbles, and 7 yellow marbles. You randomly select three marbles from the bag. What is the probability that all three marbles are red when (a) you replace each marble before selecting the next marble, and (b) you do not replace each marble before selecting the next marble?

Answer 1

a) pr(3red, replacement)=(9/20)^3
b) pr(3red, wo replacement)=9/20 * 8/19*7/18