posted by dan on .
A bag of marbles has 5 Green, 4 Red, and 3 yellow marbles. Three marbles are randomly drawn from the bag, without replacement: What is the probability that at least one of the three marbles drawn are red? What is the probability that only one of the three marbles drawn is red? What is the probability that more than one of the three marbles are red?
At least one red = one, two or three reds = 4/12 * 3/11 * 2/10 = P (three reds)
4/12 * 3/11 * 8/10 = P (two reds)
4/12 * 8/11 * 7/10 = P (one red)
Either-or probability is found by adding the individual probabilities.
The above data can be used to answer all three questions.