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Old 11-03-2007, 02:53 AM
David Sklansky David Sklansky is offline
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Join Date: Aug 2002
Posts: 5,092
Default Re: help with math problem

More simply put:

The chances you picked the first hat and got two blues is 1/2 x 2/10 x 1/9 or 2/180.

The chances you picked the second hat and got two blues is 1/2 x 8/10 x 7/9 or 56/180.

You are going to get two blues 58 out of 180 times. When you do, there is a 56 out of 58 chance it came from the second hat.

So there is a 56/58 chance that you are looking at an 8/10 probability (to pick a red) and a 2/58 chance you are looking at a 2/10 probability.

56/58 x 8/10 plus 2/58 x 2/10 is 452/580.
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