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Best Answer witzar, 15 February 2013 - 01:26 PM

Spoiler for my guess

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#1 bonanova

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Posted 15 February 2013 - 04:57 AM

A velvet bag contains 9 black marbles and 6 white ones.

You draw them from the bag, one at a time.

When you are finished you have, of course, more black marbles than white.

 

What is the probability that, in addition, after each draw you have drawn cumulatively more black marbles than white?


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#2 witzar

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Posted 15 February 2013 - 01:26 PM   Best Answer

Spoiler for my guess


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#3 bonanova

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Posted 15 February 2013 - 11:13 PM

Spoiler for my guess

 

Well done. It might be of interest if you have a concise proof?


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#4 witzar

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Posted 16 February 2013 - 04:47 PM

Unfortunately not. I just wrote a recurrent equation (to count possible arrangements of marbles) and solved it using computer.


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