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NNTP-Posting-Date: Tue, 13 Dec 2011 11:15:35 -0600
Message-ID: <4EE78837.2A2C@mindspring.com>
Date: Tue, 13 Dec 2011 12:15:35 -0500
From: pete <pfiland@mindspring.com>
Reply-To: pfiland@mindspring.com
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Subject: Re: Toughest Probability Question
References: <9cb0f967-18d1-410c-9074-f4d84858d9af@u10g2000prl.googlegroups.com> <4EE69C7E.12EB@mindspring.com> <slrnjedm5u.2as3.usenet-nospam@guild.seebs.net>
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Xref: x330-a1.tempe.blueboxinc.net comp.lang.c:14561

Seebs wrote:
> 
> On 2011-12-13, pete <pfiland@mindspring.com> wrote:
> > divya bisht wrote:
> >> How many people must be gathered together in a room,
> >> before you can be
> >> certain that there is a greater than 50/50 chance
> >> that at least two of
> >> them have the same birthday?
> 
> >> Discuss Solution in link below
> 
> > The probability that 23 random birthdays are all different is 0.492703
> 
> So?

I made a mistake in the program.

This line:

    printf("The probability that %d "
        "random birthdays are all different is %f\n", 
        people, probability);

should have been written as:

    printf("The probability that %d "
        "random birthdays are all different is %f\n", 
        people, 1.0 - probability);

and the output should have been :

 The probability that 23 random birthdays are all different is 0.507297

intstead.

-- 
pete