document.write( "Question 1008472: a man drives for 90 miles in the city, when he gets to the highway he increased his speed by 20 mph and drove for 130 miles. if he drove for 4 hours how fast did he drive in the city \n" ); document.write( "
Algebra.Com's Answer #624137 by stanbon(75887)\"\" \"About 
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a man drives for 90 miles in the city, when he gets to the highway he increased his speed by 20 mph and drove for 130 miles. if he drove for 4 hours how fast did he drive in the city
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\n" ); document.write( "City DATA:
\n" ); document.write( "distance = 90 miles ; rate = r mph ; time = d/r = 90/r hrs
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\n" ); document.write( "Hiway DATA:
\n" ); document.write( "distance = 130 miles ; rate = (r+20) mph ; time = 130/(r+20) hrs
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\n" ); document.write( "Equation::
\n" ); document.write( "90/r + 130/(r+20) = 4 hrs
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\n" ); document.write( "90(r+20) + 130r = 4r(r+20)
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\n" ); document.write( "220r + 1800 = 4r^2 + 80r
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\n" ); document.write( "4r^2 -140r - 1800 = 0
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\n" ); document.write( "r^2 - 35r - 450 = 0
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\n" ); document.write( "Ans: r = 45 mph (City speed)
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\n" ); document.write( "Cheers,
\n" ); document.write( "Stan H.
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