document.write( "Question 1170634: Janet is 6 years older than her sister Rose. In 10 years time, Rose will just be a third of his father's age. Given that their total age is 81. Find their present age. \n" ); document.write( "

Algebra.Com's Answer #795511 by ikleyn(52777) $\"\"$ $\"About$

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\n" ); document.write( "Janet is 6 years older than her sister Rose. In 10 years time, Rose will just be a third of his father's age.
\n" ); document.write( "Given that their total age is 81. Find their present age.
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document.write( "Let x be the Rose's age in 10 years time from now.\r\n" );
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document.write( "Then the Janet's age in 10 years from now is  (x+6) years, and\r\n" );
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document.write( "     the father's age in 10 years from now will be thrice the Rose's age, i.e. 3x years.\r\n" );
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document.write( "For the total of their ages 10 years from now we have THIS equation\r\n" );
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document.write( "    x + (x+6) + 3x = 81.\r\n" );
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document.write( "Simplify and find x\r\n" );
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document.write( "    5x = 81 - 6\r\n" );
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document.write( "    5x = 75\r\n" );
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document.write( "     x = 75/5 = 15.\r\n" );
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document.write( "So, Rose's age will be 15 years in 10 years from now;\r\n" );
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document.write( "    hence, her present age is 15-10 = 5 years.\r\n" );
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document.write( "Then her sister Janet is  5+6 = 11 years old, and the father is 3*(5+10) = 45 years old.\r\n" );
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document.write( "ANSWER.  Their current age is 5 years (Rose);  11 years (Janet)  and  45 years (the father).\r\n" );
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document.write( "CHECK.  In 10 years the sum of their ages will be  (5+10) + (11+10) + (45+10) = 15+21+55 = 91 years.   ! Correct !\r\n" );
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\n" ); document.write( "\n" ); document.write( "The lesson to learn from my post is THIS:\r
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\n" ); document.write( "\n" ); document.write( " Choose the unknown/unknowns by a rational way to facilitate the solution (!)\r
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