document.write( "Question 86544: It takes Peter 15 minutes longer than Charles to mow the lawn by himself. Together, they can mow the lawn in 18 minutes. How long will it take Charles to mow the lawn by himself? \n" ); document.write( "
Algebra.Com's Answer #62604 by ankor@dixie-net.com(22740)\"\" \"About 
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It takes Peter 15 minutes longer than Charles to mow the lawn by himself. Together, they can mow the lawn in 18 minutes. How long will it take Charles to mow the lawn by himself?
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\n" ); document.write( "Let t = time required by Charles to mow by himself
\n" ); document.write( "Then
\n" ); document.write( "(t+15) = time required by Peter to do it by himself
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\n" ); document.write( "Let the completed job = 1:
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\n" ); document.write( "\"18%2F%28%28t%2B15%29%29\" + \"18%2Ft\" = 1
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\n" ); document.write( "Multiply equation by t(t+15)
\n" ); document.write( "18t + 18(t+15) = t(t+15)
\n" ); document.write( "18t + 18t + 270 = t^2 + 15t
\n" ); document.write( "36t + 270 = t^2 + 15t
\n" ); document.write( "0 = t^2 + 15t - 36t - 270
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\n" ); document.write( "t^2 - 21t - 270 = 0; a quadratic equation
\n" ); document.write( "Factors to:
\n" ); document.write( "(t - 30)(t + 9) = 0
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\n" ); document.write( "t = +30 min; this is the solution that makes sense
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\n" ); document.write( "Check:
\n" ); document.write( "18/30 + 18/45 =
\n" ); document.write( " .6 + .4 = 1\r
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