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From: jmann@ihuxo.UUCP
Newsgroups: net.misc,net.flame
Subject: RE: simple stat problem
Message-ID: <278@ihuxo.UUCP>
Date: Wed, 24-Aug-83 12:13:28 EDT
Article-I.D.: ihuxo.278
Posted: Wed Aug 24 12:13:28 1983
Date-Received: Fri, 26-Aug-83 01:28:12 EDT
Organization: BTL Naperville, Il.
Lines: 21

Following should clarify to the people who still think the
probability of getting a gold coin after the first gold coin is 1/2
and not 2/3. Consider this figure:
 
  |  C1  |  C2  |  C3  |
  |      |      |      |
  ----------------------
  |  G   |  G   |  S   |
  ----------------------
  |  G   |  S   |  S   |
  ----------------------
  |      |      |      |
 
The above picture has three cabinets C1, C2 and C3. Each
of the cabinet has two drawers containing a silver(S) or a
gold(G) coin. When the first opened drawer, top or bottom,
has a god coin, it is clear that we have one of the three
drawers containing a gold coin. For two of these three drawers
the other drawer in the same cabinet will have a gold coin.
Hence the probability is 2/3. The tricky part is to consider
both the upper and lower drawers.