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  #1  
Old 09-27-2006, 10:31 PM
zigzag zigzag is offline
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Join Date: Jul 2006
Posts: 8
Default Really simple question

I have no idea how to figure out this really simple question.

Deal 5 cards out. What percent of the time will there be an ace?

What if you deal 10 cards out?
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  #2  
Old 09-27-2006, 10:48 PM
bigpooch bigpooch is offline
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Join Date: Sep 2003
Location: Hong Kong
Posts: 1,330
Default Re: Really simple question

The simplest way to think about this is to determine when
you WILL NOT GET AN ACE.

For five cards, to NOT get an ace, the first card MUST NOT
be an ace and that probability is 48/52. Then, the second
card is not an ace with a probability of 47/51, etc. You
then simply multiply; if you punch it in a calculator, the
odds of NOT getting an ace if you deal five cards is about
0.658842 and for ten cards, it's about 0.413445. The odds
of GETTING AN ACE is just 1-Prob(not getting an ace).

With combinatorics, it's a bit easier: if C(n,r) = the
number of combinations of n things chosen r at a time, the
odds of not getting an ace in k cards is simply
C(48,k)/C(52,k) where k is any integer between 0 and 52
inclusive.
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