In a contest, there are 9 identical boxes: in 7 boxes there are a $50 bill into each box, and in 2 boxes there are a $100 bill into each one. To win and get the money picked, you have to choose two boxes that contain different bills. What is the probability to win?  Choose the correct choice
A) 2/9  B) 1/9  C) 49/1296  D) 7/36  E) 7/18
We are told that we have 9 identical boxes, 7 of $50 and 2 of $100. The bills are picked simultaneous and randomly, B1 and B2, in different flavors. There are two acceptable outcomes: 1) B1 is $50 and B2 is $100; 2) B1 is $100 and B2 is $50. Let's go: 1) B1 = (7/9)(2/8)= 7/36 chance of this happening. 2) B2 = (2/9)(7/8) = 7/36 chance of this happening. Then: (7/36)+(7/36)= 7/18, chance of getting the result that you wanted. Answer 7/18.
<result>E</result>
In a contest, there are 9 identical boxes: in 7 boxes there are a $50 bill into each box, and in 2 boxes there are a $100 bill into each one. To win and get the money picked, you have to choose two boxes that contain different bills. What is the probability to win?