document.write( "Question 956308: Mark walks 3 miles to the house of a friend and returns home on a bike. He averages 5 mph faster when cycling than walking, and the total time for both trips is 2 hours. Find his walking speed.\r
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Algebra.Com's Answer #584243 by ptaylor(2198)![]() ![]() You can put this solution on YOUR website! Mark walks 3 miles to the house of a friend and returns home on a bike. He averages 5 mph faster when cycling than walking, and the total time for both trips is 2 hours. Find his walking speed.\r \n" ); document.write( "\n" ); document.write( "Distance(d) equals Rate(r) times Time(t) or d=rt; r=d/t and t=d/r\r \n" ); document.write( "\n" ); document.write( "Let r=Mark's walking speed \n" ); document.write( "Then r+5=Marks cycling speed \n" ); document.write( "Time that Mark walked plus time that Mark cycled equals 2 hrs \n" ); document.write( "Time Mark walked=3/r \n" ); document.write( "Time Mark cycled=3/(r+5) \n" ); document.write( "Soooo: \n" ); document.write( "3/r + 3/(r+5)=2 multiply each term by r(r+5) \n" ); document.write( "3(r+5)+3r=2r(r+5) expand \n" ); document.write( "3r+15+3r=2r^2+10r simplify \n" ); document.write( "2r^2+10r-6r-15=0 \n" ); document.write( "2r^2+4r-15=0 Solve using the quadratic formula \n" ); document.write( "r=(-b+-sqrt(b^2-4ac))/2a \n" ); document.write( "r=(-4+-sqrt(16-4*2*(-15))/4 \n" ); document.write( "r=(-4+-sqrt(136))/4 \n" ); document.write( "r=(-4+-11.66)/4 negative answer is no good. The positive answer is \n" ); document.write( "r=7.66/4=~~~1.92 mph---walking speed\r \n" ); document.write( "\n" ); document.write( "Hope this helps----ptaylor\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( " \n" ); document.write( " |