A jar contains 3 black, 3 white and 1 green balls. If you pick two balls at the same time, what's the probability that one ball is black and one is white?	Select
A) 2/7
B) 5/7
C) 4/7
D) 3/7
E) 1/2
P(1st black, 2nd white) = 3/7*3/6 = 9/42;   P(1st white, 2nd black) = 3/7*3/6 = 9/42.   P = 9/42 + 9/42 = 18/42 = 3/7.   Answer: 3/7.
<result>D</result>
A jar contains 3 black, 3 white and 1 green balls. If you pick two balls at the same time, what's the probability that one ball is black and one is white?