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Old 05-08-2006, 03:01 PM
_TKO_ _TKO_ is offline
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Join Date: Jul 2005
Location: Toronto, Ontario, Canada
Posts: 6,160
Default Recursive Probability?

Let's say the situation is this:
There is a bag containing 10 marbles. There are 3 red marbles, 3 green marbles, 3 blue marbles, and 1 "special" marble. You get to pick two marbles out of the bag. If you draw the special marble, then two things happen:
1. You must put the special marble back in the bag.
2. You get to pick two more marbles, regardless of how many picks you have already had (ie: If you draw the special marble on your first pick, you get to pick two more marbles, and if you draw the special marble on your second pick, you still only get to pick two more marbles).

What is the probability that you will end up with two red marbles, and how do you calculate this?
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