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Subj:.....The Price Of Eggs (S638) 
          From the book 
            "More Mathematical Puzzles
             of Sam Loyd" 
          Edited by Martin Gardner 
          From: Dover Publications in 1960

Drawing from
Karen's Art Page

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"I paid twelve cents for the eggs I bought from the grocer," 
explained the cook, "but I made him throw in two extra eggs 
because they were so little.  That made the lot cost just 
one cent per dozen less than the first asking price." 

How many eggs did the cook buy?

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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
 

The cook bought sixteen eggs, but the grocer threw in
two extra eggs, making eighteen in all.

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My solution is the following:

Let X = the original number of eggs

The equation becomes

   Original price per dozen - One  =  New price per dozen

   Creating the equation from the word equation yields

   12               12                      144             144
  _____  -  1  =  _____  which reduces to  _____  -  1  =  _____

    X             X + 2                      X             X + 2
   __             _____
   12              12

   Multiplying both sides of the equation by the common

   denominator of  X ( X + 2 ) yields

   144 ( X + 2 )  -  1 X ( X + 2 )  =  144 X

   Multiplying

   144 X  +  288  -  X²  +  2 X  =  144 X

   Moving everything to the right side of the equation yields

   0  =  X²  -  2 X  - 288

   Factoring

   0  =  ( X - 18 ) ( X + 16 )

   Setting each factor equal to zero yields

   X  =  16  or  - 18

   Therefore the answer is the cook bought sixteen eggs.

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