document.write( "Question 335060: John drives from Town A to Town B , a distance of 720 km , at a constant speed. When he returns from Town B to A, he saves an hour of travel time by increasing his average speed by 10 km/h. find the total time taken for the whole journey(to and fro) \n" ); document.write( "
Algebra.Com's Answer #240128 by stanbon(75887)\"\" \"About 
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John drives from Town A to Town B , a distance of 720 km , at a constant speed.
\n" ); document.write( "distance = 720 km ; rate = x km/h ; time = 720/x hrs.
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\n" ); document.write( "\n" ); document.write( "When he returns from Town B to A, he saves an hour of travel time by increasing his average speed by 10 km/h.
\n" ); document.write( "distance = 720 km ; rate = (x+10) km/h ; time = 720/(\r
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\n" ); document.write( "\n" ); document.write( "Find the total time taken for the whole journey(to and fro)
\n" ); document.write( "Equation:
\n" ); document.write( "time to - time from = 1 hr
\n" ); document.write( "720/x - 720/(x+10) = 1
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\n" ); document.write( "Multiply thru by x(x+10) to get:
\n" ); document.write( "720(x+10) - 720x = x(x+10)
\n" ); document.write( "7200 = x^2+10x
\n" ); document.write( "x^2+10x-7200 = 0
\n" ); document.write( "(x+90)(x-80) = 0
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\n" ); document.write( "x = 80 km/h ; time to = 720/80 = 9 hrs.
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\n" ); document.write( "x+10 = 90 km/h ; time from = 720/90 = 8 hrs.
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\n" ); document.write( "Total time = 9+8 = 17 hrs.\r
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\n" ); document.write( "Cheers,
\n" ); document.write( "Stan H.
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