I don't know if you already found it but however...

http://www.milaadesign.com/wizardy.html

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scary  

A stormy  night

Three men arrive at a   seedy  rural Motel.  
"We want 3 rooms".  The shady desk clerk   replies "That'll be $10 -each.  
"  Each man hands the clerk a $10 bill, they take their keys,
and retire to their rooms for the night.

Minutes later  The desk clerk decides   -"I over-charged those guys.  
Those crappy rooms aren't worth $10."   He calls over the bell boy
"Here take this $5 and give those guys
       some of their money back..."

On the way over the Bell clerk thinks "Hey I can't divide $5 evenly
among 3 guys, and they don't know how much money
 I'm supposed to give back."  
       he pockets -$2,    and gives each man
       back   -a dollar.

OKAY Now, each man   has now paid $9  
             for his room   for the night -?

Since the Bellboy has $2, and    3  x $9   = $27
$27  + $2  =   $29

  > WHERE  did   the OTHER  dollar  -go  ? ? ?

Why $27 + $2 ? It's 27$ - $2  [$30 - ($3+$2)]

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