A jar contains 5 black and 2 white balls. If you pick two balls at the same time, what's the probability that one ball is black and one is white?
Pick one:	A) 2/7	B) 5/21	C) 4/21	D) 3/7	E) 1/2
P(1st black, 2nd white) = 5/7*2/6 = 10/42;   P(1st white, 2nd black) = 2/7*5/6 = 10/42.   P = 10/42 + 10/42 = 20/84= 10/42 = 5/21   Answer: 5/21.
<result>B</result>
A jar contains 5 black and 2 white balls. If you pick two balls at the same time, what's the probability that one ball is black and one is white?