Infinite supply of marbles probability problem

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SUMMARY

The probability problem discussed involves an infinite supply of marbles, where marble number 1 is placed in an urn alongside others in pairs. As the process continues indefinitely, the probability that marble number 1 remains in the urn is calculated as the limit of (n-1)/n as n approaches infinity. The conclusion drawn is that the probability approaches zero, indicating that marble number 1 will not remain in the urn forever. This result is confirmed by the iterative calculations provided, which demonstrate the diminishing likelihood of marble number 1's retention.

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Roni1985
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Homework Statement


A has an infinite supply of marbles numbered 1,2,3,... A places the marbles, two at a time and in numerical order, into an urn (i.e. first 1 and 2, then 3 and 4, etc.). Each time A puts two marbles, B reaches in and pulls on out. This process goes on forever.

c) If B always removes marbles randomly (each marble in the urn equally likely to e removed), with what probability will marble number 1 remain in the urn forever?


Homework Equations





The Attempt at a Solution


Here is what I did:
1,2 =>prob that 1 stays is 1/2

1,3,4 => prob that 1 stays is 2/3

1,3,4,6 =>prob that 1 stays is 3/4

until (n-1)/n

so we need to multiply them all and we are left with 1/n
so as n->inf, the probability that it happens is zero ?

Is my answer correct ?

Thanks,
Roni.
 
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Seems fine to me.
 


Dick said:
Seems fine to me.

I see, thanks very much :)
 

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