document.write( "Question 861017: It takes a small sprinkler 12 min longer to soak a lawn than it takes a large sprinkler. Working together, the sprinklers can soak the lawn in 8 min. How long would it take each sprinkler, working alone, to soak the lawn?
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document.write( "small sprinkler
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document.write( "large sprinkler ______ min. \r
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Algebra.Com's Answer #518885 by ankor@dixie-net.com(22740)![]() ![]() You can put this solution on YOUR website! It takes a small sprinkler 12 min longer to soak a lawn than it takes a large sprinkler. \n" ); document.write( " Working together, the sprinklers can soak the lawn in 8 min. \n" ); document.write( " How long would it take each sprinkler, working alone, to soak the lawn? \n" ); document.write( ": \n" ); document.write( "let t = time required by the larger sprinkler \n" ); document.write( "then \n" ); document.write( "(t+12) = time required by the small \n" ); document.write( ": \n" ); document.write( "the completed job = 1 (a soaked lawn) \n" ); document.write( ": \n" ); document.write( "Each will do a fraction of the job, the two fractions add up to 1 \n" ); document.write( " \n" ); document.write( "multiply by t(t+12) to clear the denominators, results: \n" ); document.write( "8(t+12) + 8t = t(t+12) \n" ); document.write( "8t + 96 + 8t = t^2 + 12t \n" ); document.write( "combine to form a quadratic on the right \n" ); document.write( "0 = t^2 + 12t - 16t - 96 \n" ); document.write( "t^@ - 4t - 96 = 0 \n" ); document.write( "Factors to \n" ); document.write( "(t-12)(t+8) = 0 \n" ); document.write( "positive solution \n" ); document.write( "t = 12 min for the larger sprinkler \n" ); document.write( "and \n" ); document.write( "12 + 12 = 24 min for the small one\r \n" ); document.write( "\n" ); document.write( " \n" ); document.write( " |