document.write( "Question 599502: The stopping distance of a car after the brakes have been applied varies directly with the square of the speed. If a car traveling at 60 mph can stop in 180 ft., what is the distance needed to stop the same car traveling at 72 mph? \n" ); document.write( "
Algebra.Com's Answer #378979 by nerdybill(7384)\"\" \"About 
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The stopping distance of a car after the brakes have been applied varies directly with the square of the speed. If a car traveling at 60 mph can stop in 180 ft., what is the distance needed to stop the same car traveling at 72 mph?
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\n" ); document.write( "When you see \"direct variation\" think:
\n" ); document.write( "y = kx
\n" ); document.write( "where k is a constant.
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\n" ); document.write( "We find that constant from: \"If a car traveling at 60 mph can stop in 180 ft\"
\n" ); document.write( "y = kx
\n" ); document.write( "180 = k(60)
\n" ); document.write( "180/60 = k
\n" ); document.write( "3 = k
\n" ); document.write( ".
\n" ); document.write( "Our general formula then is:
\n" ); document.write( "y = 3x
\n" ); document.write( ".
\n" ); document.write( "now, we can answer:
\n" ); document.write( "what is the distance needed to stop the same car traveling at 72 mph?
\n" ); document.write( "y = 3(72)
\n" ); document.write( "y = 216 feet \n" ); document.write( "
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