With a bag of 5 blue marbles, 7 green marbles, and 3 red marbles. What is the probability of picking out two blue marbles? Pick them one at a time and do not replace them.

So there are 15 marbles in total (5 + 7 + 3) The probability of the first marble will be the number of blue marbles / total number of marblesTherefore, you do 5/15 = 1/3 Then for the second marble you do the same. But there are only 4 blue marbles left and 14 in total, so you do 4/14.Because these events are AND events. Probability of picking out a blue first time AND second time. You multiply the two probabilities 1/3 * 4/14 = 2/21