document.write( "Question 853754: a man drove at a constant speed from his city 180 miles away. On the return trip, he increased his constant speed by 5 mph and made the return trip in 24 minutes less time than had been required to drive to the city. What was his sped from home to the city? \n" ); document.write( "

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a man drove at a constant speed from his city 180 miles away. On the return trip, he increased his constant speed by 5 mph and made the return trip in 24 minutes less time than had been required to drive to the city. What was his sped from home to the city?
\n" ); document.write( "***
\n" ); document.write( "let x=speed from home to city
\n" ); document.write( "x+5=speed on return trip
\n" ); document.write( "travel time=distance/speed
\n" ); document.write( "..
\n" ); document.write( "24 min=24/60=2/5 hr
\n" ); document.write( " $\"180%2Fx-180%2F%28x%2B5%29=2%2F5\"$
\n" ); document.write( "LCD:5x(x+5)
\n" ); document.write( "5(180x+900)-900x=2x(x+5)
\n" ); document.write( "900x+4500-900x=2x^2+10x
\n" ); document.write( "2x^2+10x-4500=0
\n" ); document.write( "x^2+5x-2250=0
\n" ); document.write( "(x+50)(x-45)=0
\n" ); document.write( "x=-50 (reject)
\n" ); document.write( "or
\n" ); document.write( "x=45
\n" ); document.write( "speed from home to city=45 mph \n" ); document.write( "

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