John has 6 green marbles and 4 purple marbles. He chooses a marble at random, writes down its color, and then puts the marble back. He performs this process 5 times. What is the probability that he chooses exactly two green marbles?
Here's my best effort.......
Out of any 5 marbles drawn, 2 need to be green.....and the probability of a green on any draw is 6/10
So we have :
C(5,2) * (.6)^2 * (.4)^3 = 144/625 = 23.04 %
+194 
