document.write( "Question 168173: It takes Lucy 15 minutes longer to clean her garage alone than it takes her brother Billy. Together they can clean the garage in 4 minutes. If Lucy were cleaning the garage alone, how long would it take her to complete the job? \n" ); document.write( "
Algebra.Com's Answer #123931 by ankor@dixie-net.com(22740)![]() ![]() You can put this solution on YOUR website! : \n" ); document.write( "It takes Lucy 15 minutes longer to clean her garage alone than it takes her brother Billy. \n" ); document.write( ": \n" ); document.write( "Together they can clean the garage in 4 minutes. \n" ); document.write( ": \n" ); document.write( "If Lucy were cleaning the garage alone, how long would it take her to complete the job? \n" ); document.write( ": \n" ); document.write( "Let x = L's time (in minutes) working alone \n" ); document.write( "then \n" ); document.write( "(x-15) = B's time working alone \n" ); document.write( ": \n" ); document.write( "Let the completed job = 1 \n" ); document.write( ": \n" ); document.write( " \n" ); document.write( ": \n" ); document.write( "Multiply equation by x(x-15) to get rid of the denominators, results: \n" ); document.write( "4x + 4(x-15) = x(x-15) \n" ); document.write( ": \n" ); document.write( "4x + 4x - 60 = x^2 - 15x \n" ); document.write( ": \n" ); document.write( "8x - 60 = x^2 - 15x \n" ); document.write( ": \n" ); document.write( "Arrange as a quadratic equation: \n" ); document.write( "x^2 - 15x - 8x + 60 = 0 \n" ); document.write( ": \n" ); document.write( "x^2 - 23x + 60 = 0 \n" ); document.write( "Factor this to: \n" ); document.write( "(x - 3)(x - 20) \n" ); document.write( ": \n" ); document.write( "x = 3 does not make sense \n" ); document.write( ": \n" ); document.write( "x = 20 min, L's time working alone. \n" ); document.write( ": \n" ); document.write( ": \n" ); document.write( "Check solution; B's time would be 20 - 15 = 5 min \n" ); document.write( " |