document.write( "Question 224698: A cyclist rides 30 miles at an average speed of 9 miles/hr. At what rate must the cyclist cover the next 10 miles in order to bring the overall average speed up to 10 miles/hr? \n" ); document.write( "

Algebra.Com's Answer #167838 by ankor@dixie-net.com(22740) $\"\"$ $\"About$

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A cyclist rides 30 miles at an average speed of 9 miles/hr.
\n" ); document.write( " At what rate must the cyclist cover the next 10 miles in order to bring the
\n" ); document.write( "overall average speed up to 10 miles/hr?
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\n" ); document.write( "Let s = speed required to accomplish this
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\n" ); document.write( "In order accomplish this the total time for the 40 mi trip:
\n" ); document.write( " $\"40%2F10\"$ = 4 hrs
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\n" ); document.write( "Write a time equation (time = $\"+dist%2Fspeed\"$ ):
\n" ); document.write( "Time at 9 mph + time at s mph = 4 hrs
\n" ); document.write( " $\"30%2F9\"$ + $\"10%2Fs\"$ = 4
\n" ); document.write( "Multiply by 9s, results
\n" ); document.write( "30s + 9(10) = 9s(4)
\n" ); document.write( "30s + 90 = 36s
\n" ); document.write( "90 = 36s - 30s
\n" ); document.write( "90 = 6s
\n" ); document.write( "s = $\"90%2F6\"$
\n" ); document.write( "s = 15 mph in order to average 10 mph
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\n" ); document.write( ":
\n" ); document.write( "Check solution by finding the times = 4 hr
\n" ); document.write( "30/9 + 10/15 =
\n" ); document.write( "3.33 = .67 = 4 hrs
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