A jar contains 4 black and 3 white 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) = 4/7*3/6 = 4/14;   P(1st white, 2nd black) = 3/7*4/6 = 4/14.   P = 4/14 + 4/14 = 4/7.   Answer: 4/7.
<result>C</result>
A jar contains 4 black and 3 white balls. If you pick two balls at the same time, what's the probability that one ball is black and one is white?