April 2nd, 2009, 03:34 PM  #1 
Newbie Joined: Feb 2009 Posts: 8 Thanks: 0  how calculate
8C2 ? is a combination ;P  one marble is randomly drawn, and then NOT REPLACED, from a jar containing two white marbles and one black marble. A second marble is drawn. what is the probability of drawing a white one and then black one ? explain pls because idk how to explain 
April 2nd, 2009, 03:52 PM  #2 
Global Moderator Joined: May 2007 Posts: 6,805 Thanks: 716  Re: how calculate
Prob of drawing white marble first is 2/3. In that case you have one white and one black left so prob. of drawing black is 1/2. So prob. of both together is 1/3.

April 2nd, 2009, 04:01 PM  #3 
Newbie Joined: Feb 2009 Posts: 8 Thanks: 0  Re: how calculate
thnks .. 8 combination 2 ? 
April 2nd, 2009, 10:03 PM  #4 
Global Moderator Joined: Dec 2006 Posts: 20,919 Thanks: 2203 
Use a Google search to find out how to calculate 8C2. You are not given enough information to allow the probability question to be answered. The answer mathman gave relied on a significant unstated assumption; can you identify what that assumption was?


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