A jar contains 28 marbles. It has 10 red, 8 black and 10 green marbles. Two marbles are drawn, the first is not returned before the second one is drawn. What is the probability that both marbles are green?
Probability of green marble on first draw = 10/28 = 5/14
Probability of drawing a green marble on the second draw = 9/27 = 1/3
So....probability that both marbles are green is 5/14 * 1/3 = 5 / 42