document.write( "Question 426723: a bicyclist leaves a point and then a car leaves the same point 2 hours later going 12mph faster. After 90 miles the car catches the bicyclist. Find the speed of both the car and the bicyclist. \n" ); document.write( "
Algebra.Com's Answer #296829 by ankor@dixie-net.com(22740)\"\" \"About 
You can put this solution on YOUR website!
a bicyclist leaves a point and then a car leaves the same point 2 hours later going 12mph faster.
\n" ); document.write( " After 90 miles the car catches the bicyclist.
\n" ); document.write( " Find the speed of both the car and the bicyclist.
\n" ); document.write( ":
\n" ); document.write( "Let s = the bike speed
\n" ); document.write( "then
\n" ); document.write( "(s+12) = the car speed
\n" ); document.write( ":
\n" ); document.write( "Write a time equation: time = dist/speed
\n" ); document.write( ":
\n" ); document.write( "Bike time = Car time + 2 hrs
\n" ); document.write( "\"90%2Fs\" = \"90%2F%28%28s%2B12%29%29\" + 2
\n" ); document.write( ":
\n" ); document.write( "Multiply by s(s+12), results
\n" ); document.write( "90(s+12) = 90s + 2s(s+12)
\n" ); document.write( ":
\n" ); document.write( "90s + 1080 = 90s + 2s^2 + 24s
\n" ); document.write( ":
\n" ); document.write( "Arrange as a quadratic equation on the right
\n" ); document.write( "0 = 90s - 90s + 2s^2 + 24s - 1080
\n" ); document.write( ":
\n" ); document.write( "2s^2 + 24s - 1080 = 0
\n" ); document.write( ":
\n" ); document.write( "Simplify,divide by 2
\n" ); document.write( "s^2 + 12s - 540 = 0
\n" ); document.write( "Factors to
\n" ); document.write( "(s-18)(s+30) = 0
\n" ); document.write( "the positive solution
\n" ); document.write( "s = 18 mph is the bike speed
\n" ); document.write( "then
\n" ); document.write( "18 + 12 = 30 mph is the car's
\n" ); document.write( ":
\n" ); document.write( ":
\n" ); document.write( "Check solution by finding the actual travel time of each
\n" ); document.write( "90/18 = 5 hrs
\n" ); document.write( "90/30 = 3 hrs
\n" ); document.write( "--------------
\n" ); document.write( "a diff of 2 hrs
\n" ); document.write( "
\n" );