document.write( "Question 975668: To save fuel on the 240 km trip to their cottage, the smith family reduce their usual average speed by 20 km/h. This meant that their trip took 1 hour more than usual. What is their average speed? \n" ); document.write( "
Algebra.Com's Answer #597374 by stanbon(75887)\"\" \"About 
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To save fuel on the 240 km trip to their cottage, the smith family reduce their usual average speed by 20 km/h. This meant that their trip took 1 hour more than usual. What is their average speed?
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\n" ); document.write( "Faster trip DATA:
\n" ); document.write( "distance = 240 km ; rate = r km/hr ; time = d/r = 240/r hrs
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\n" ); document.write( "Slower trip DATA:
\n" ); document.write( "distance = 240 km ; rate = r-20 km/hr ; time = 240/(r-20) hrs
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\n" ); document.write( "Equation:
\n" ); document.write( "slower time - faster time = 1 hr
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\n" ); document.write( "240/(r-20) - 240/r = 1
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\n" ); document.write( "240r - 240r + 240*20 = r(r-20)
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\n" ); document.write( "r^2 - 20r - 20*240 = 0
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\n" ); document.write( "Ans: r = 80 km/hr
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\n" ); document.write( "Cheers,
\n" ); document.write( "Stan H.
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