document.write( "Question 515123: A boy says \"I have the same number of sisters as I have brothers\".
\n" ); document.write( "His sister says \"I have twice as many brothers as I have sisters\".
\n" ); document.write( "How many sons and how many daughters do their parents have?
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Algebra.Com's Answer #343747 by Edwin McCravy(20055) $\"\"$ $\"About$

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A boy says \"I have the same number of sisters as I have brothers\".
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\n" ); document.write( "How many sons and how many daughters do their parents have?
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document.write( "Let S = the number of sons\r\n" );
document.write( "Let D = the number of daughters\r\n" );
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document.write( "The number of sisters the boy has is the same as the number of daughters.\r\n" );
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document.write( "The number of brothers the boy has is 1 less than the number of sons,\r\n" );
document.write( "because he is not his own brother.\r\n" );
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document.write( "The number of brothers the girl has is the same as the number of sons.\r\n" );
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document.write( "The number of sisters the girl has is 1 less than the number of daughters,\r\n" );
document.write( "because she is not her own sister.\r\n" );
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document.write( "So,\r\n" );
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document.write( "NUMBER OF HIS SISTERS = NUMBER OF DAUGHTERS\r\n" );
document.write( "NUMBER OF HIS BROTHERS = NUMBER OF SONS - 1 \r\n" );
document.write( "NUMBER OF HER BROTHERS = NUMBER OF SONS\r\n" );
document.write( "NUMBER OF HER SISTERS = NUMBER OF DAUGHTERS - 1\r\n" );
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document.write( "The first equation comes from:\r\n" );
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document.write( "NUMBER OF HIS SISTERS = NUMBER OF HIS BROTHERS \r\n" );
document.write( "  NUMBER OF DAUGHTERS = NUMBER OF SONS - 1\r\n" );
document.write( "                    D = S - 1\r\n" );
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document.write( "The second equation comes from:\r\n" );
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document.write( "NUMBER OF HER BROTHERS = 2*(NUMBER OF HER SISTERS) \r\n" );
document.write( "        NUMBER OF SONS = 2*(NUMBER OF DAUGHTERS - 1)\r\n" );
document.write( "                     S = 2(D - 1)\r\n" );
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document.write( "       Solve the system of equations:\r\n" );
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document.write( "                     D = S - 1\r\n" );
document.write( "                     S = 2(D - 1)\r\n" );
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document.write( "Solve that and get D = 3, S = 4.\r\n" );
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document.write( "So their parents have 3 daughters and 4 sons.\r\n" );
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document.write( "Edwin

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