You have fifty coins totaling $1.00.  You drop one down an
open drain while tossing the coins in your hand.  What is
the chance that you have lost a quarter?

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Finger pointing down from darrell94590 on 1/2/2006

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Drawing from Ripleys-Believe It Or Not

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              THE SOLUTION
 

There are two ways you can have fifty coins totaling $1.00;
two dimes, forty pennies, and eight nickels; or two dimes,
forty-five pennies, two nickels, and one quarter.  These
arrangements are equally probable, so there is a one­half
chance you had a quarter to begin with.  The probability
that you then dropped that quarter from all the coins in
your hand is one fiftieth.  Therefore, the total probability
that you lost a quarter is one half times one fiftieth, or
one one-hundredth.