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Re: Insoluble marbles-in-urn problem?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg119985] Re: Insoluble marbles-in-urn problem?
  • From: Ray Koopman <koopman at sfu.ca>
  • Date: Mon, 4 Jul 2011 06:43:52 -0400 (EDT)
  • References: <iup8dp$ksp$1@smc.vnet.net>

On Jul 3, 1:14 am, John Feth <johnf... at gmail.com> wrote:
> There is a huge urn full of marbles, each marked with a single digit:
> 0, 1, 2, 3, 4, 5, 6, 7, 8, or 9.  The marked marble quantities are
> uniformly distributed between all of the digits and the marbles are
> thoroughly mixed.  You look away, choose 10 marbles, and put them in
> a black velvet bag.
>
> When you have some time, you look away, open the bag, and remove one
> marble.  You close the bag, look at the digit on the marble, open a
> beer perhaps, and calculate the probability that there is at least
> one more marble in the bag with the same digit.

P(at least one more marble with the same digit) =
1 - P(no more marbles with the same digit) =
1 - (9/10)^9 = .612579511


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