document.write( "Question 1060146: A runner traveled 3 miles in the same time that a cyclist traveled 10 miles. The speed of the cyclist was 14 mph greater than that of the runner. What was the cyclists speed?\r
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document.write( "The answer is supposed to be 20. I have tried everything I can think of but keep coming up with decimals. \n" );
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Algebra.Com's Answer #675137 by jim_thompson5910(35256)![]() ![]() ![]() You can put this solution on YOUR website! \n" ); document.write( "\"What was the cyclists speed?\" is the ultimate question here. Since it's unknown and we want to find it, let's make\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "x = cyclists speed in miles per hour.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "The runner is 14 mph slower than the cyclist, so the runner's speed is x-14 miles per hour.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "-----------------------------------------------------------------------\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "We will use the formula\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "distance = rate*time\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "\"rate\" is another term for \"speed\". In short, \r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "d = r*t\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "The distance for the runner is 3 miles. So d = 3 for the runner. The value of t is unknown. Let's just leave it as t for now.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "So \n" ); document.write( "d = r*t \n" ); document.write( "turns into \n" ); document.write( "3 = (x-14)*t \n" ); document.write( "after replacing the variables with the expressions set up earlier. \r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Similarly, for the cyclist, this equation \n" ); document.write( "d = r*t \n" ); document.write( "turns into \n" ); document.write( "10 = x*t\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "We can solve for t in that other equation to get\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "10 = x*t \n" ); document.write( "10/x = t \n" ); document.write( "t = 10/x\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Then let's plug that into the first equation\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "3 = (x-14)*t \n" ); document.write( "3 = (x-14)*(10/x) ... replace t with 10/x\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Now isolate x\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "3 = (x-14)*(10/x) \n" ); document.write( "3*x = (x-14)*(10/x)*x ... multiply both sides by x \n" ); document.write( "3x = 10(x-14) \n" ); document.write( "3x = 10x - 140 \n" ); document.write( "3x - 10x = -140 \n" ); document.write( "-7x = -140 \n" ); document.write( "x = 20 ... divide both sides by -7\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "So that's why the cyclist's speed is 20 mph. \r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Let me know if this helps or not. Thank you. \n" ); document.write( " \n" ); document.write( " |