document.write( "Question 1138531: A pet shop bought a litter of puppies for 120 pesos. All but four of them were sold, at a profit of 5 pesos each, for a total of 120 pesos. How many puppies were in the litter? \n" ); document.write( "

Algebra.Com's Answer #756323 by ikleyn(52792) $\"\"$ $\"About$

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document.write( "Let \"n\" be the number of puppies originally.\r\n" );
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document.write( "Then the buying price of each of n puppies was  .\r\n" );
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document.write( "The selling price of each of sold (n-4) puppies was  .\r\n" );
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document.write( "The profit was 5 pesos for each sold puppies, i.e.\r\n" );
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document.write( "     -  = 5    pesos.\r\n" );
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document.write( "It is your basic equation to find \"n\".  To solve the equation, multiply both sides by n*(n-4).\r\n" );
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document.write( "    120n - 120*(n-4) = 5n*(n-4)\r\n" );
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document.write( "    120n - 120n + 480 = 5n^2 - 20n\r\n" );
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document.write( "    480 = 5n^2 - 20n\r\n" );
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document.write( "    5n^2 - 20n - 480 = 0\r\n" );
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document.write( "     n^2 - 4n  -  96 = 0\r\n" );
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document.write( "     (n-12)*(n+8)    = 0\r\n" );
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document.write( "The last equation has 2 roots 12 and -8, but only positive  n= 12 is meaningful solution to the given problem.\r\n" );
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document.write( "ANSWER.  Where were 12 puppies in the litter originally.\r\n" );
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