document.write( "Question 768713: the average rate of a bus is 15 miles per hour more than that of an average truck. the truck takes 1 hour more than th bus to drive 90 miles, how long does it take the bus \n" ); document.write( "
Algebra.Com's Answer #468479 by stanbon(75887)\"\" \"About 
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the average rate of a bus is 15 miles per hour more than that of an average truck. the truck takes 1 hour more than the bus to drive 90 miles, how long does it take the bus
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\n" ); document.write( "Bus DATA:
\n" ); document.write( "distance = 90 miles ; rate = r+15 mph ; time = 90/(r+15) hrs.
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\n" ); document.write( "Truck DATA:
\n" ); document.write( "distance = 90 miles ; rate = r mph ; time = 90/r hrs.
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\n" ); document.write( "Equation:
\n" ); document.write( "truck tme - bus time = 1 hour
\n" ); document.write( "90/r - 90/(r+15) = 1
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\n" ); document.write( "90(r+15) - 90r = r^2+15r
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\n" ); document.write( "r^2 + 15r - 1350 = 0
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\n" ); document.write( "(r-30)(r+45) = 0
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\n" ); document.write( "Positive solution:
\n" ); document.write( "r = 30 mph (truck speed)
\n" ); document.write( "r+15 = 45 mph (bus speed)
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\n" ); document.write( "Cheers,
\n" ); document.write( "Stan H.
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