document.write( "Question 151407: A freight train takes 2 hours longer to travel 300 miles than an express train to travel 280 miles. The rate of the express train is 20mph greater than the rate of the freight train. Find the time for the express train.\r
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Algebra.Com's Answer #111302 by checkley77(12844)\"\" \"About 
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300=r(t+2)
\n" ); document.write( "r=300/(t+2)
\n" ); document.write( "280=(r+20)t
\n" ); document.write( "280=(300/(t+2)+20)t
\n" ); document.write( "280=300t/(t+2)+20t
\n" ); document.write( "280=(300t+20t(t+2))/(t+2)
\n" ); document.write( "280(t+2)=300t+20t^2+40t
\n" ); document.write( "280t+560=340t+20t^2
\n" ); document.write( "20t^2+340t-280t-560=0
\n" ); document.write( "20t^2+60t-560=0
\n" ); document.write( "20(t^2+3t-28)=0
\n" ); document.write( "20(t+7)(t-4)=0
\n" ); document.write( "t-4=0
\n" ); document.write( "t=4 hours for the express train
\n" ); document.write( "280=4(r+20)
\n" ); document.write( "280=4r+80
\n" ); document.write( "4r=280-80
\n" ); document.write( "4r=200
\n" ); document.write( "r=200/4
\n" ); document.write( "r=50 mph is the rate of the freight train.
\n" ); document.write( "proofs:
\n" ); document.write( "300=50(4+2)
\n" ); document.write( "300=300
\n" ); document.write( "280=(50+20)*4
\n" ); document.write( "280=70*4
\n" ); document.write( "280=280
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