document.write( "Question 1119370: Working together bob and dan complete a job in 6 hours. It would take Bob 9 hours longer than Dan to do the job alone. How long would it take Dan alone \n" ); document.write( "

Algebra.Com's Answer #734902 by ikleyn(52776) $\"\"$ $\"About$

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document.write( "Let d = \"How long would it take Dan alone\".\r\n" );
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document.write( "Then the time for Bob working alone is (d+9) hours.\r\n" );
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document.write( "The equation for \"d\" is this\r\n" );
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document.write( "     +  = 1/6            (1)\r\n" );
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document.write( "saying that the two rates of work sum up to 1/6 of the job per hour.\r\n" );
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document.write( "From (1) you get step by step\r\n" );
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document.write( "    6*(d+9) + 6d = d*(d+9) \r\n" );
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document.write( "    6d + 54 + 6d = d^2 + 9d\r\n" );
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document.write( "    d^2 - 3d - 54 = 0\r\n" );
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document.write( "    (d+6)*(d-9) = 0.\r\n" );
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document.write( "The only positive root is d = 9.\r\n" );
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document.write( "Answer.  Dan needs 9 hours to complete the job alone.\r\n" );
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document.write( "Check.    +  =  +  =  +  =  = .   ! Correct !\r\n" );
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\n" ); document.write( "\n" ); document.write( "To see other similar solved joint work problems, look into the lesson\r
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