document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1201574>Question 1201574</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The average speed of a car over a certain distance is calculated by dividing the total distance travelled by the total time taken. Two towns A and B are 10km apart, a motorist travels from A to B at an average speed of 20km per hour and travels from B to A at an average 40km per hour.<BR>\n" );
document.write( "(a) Determine the average speed to the motorist for the two trips combined. (I.e. from A to B and back to B and back to A)<BR>\n" );
document.write( "(b) Determine the speed would the motorist have to average on the return trip from B to A to yield an overall speed of 30km per hour? Assume the motorist has averaged 20km per hour from A to B<BR>\n" );
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document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #836015 by </B><A HREF=/tutors/aboutme.mpl?userid=mananth><B>mananth(16946)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=mananth><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/cgi-bin/show-face.mpl?user=mananth><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=836015\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> <BR>\n" );
document.write( "a motorist travels from A to B at an average speed of 20km per hour<BR>\n" );
document.write( "distance =10km\r<BR>\n" );
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document.write( "time = 10/20 = 0.5 hours\r<BR>\n" );
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document.write( " and travels from B to A at an average 40km per hour.\r<BR>\n" );
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document.write( "10/40 = 0.25 hours\r<BR>\n" );
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document.write( "Total time = 0.75 hours<BR>\n" );
document.write( "Total distance = 20 km\r<BR>\n" );
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document.write( "Speed = D/T = 20/0.75 = 26.67 km/h\r<BR>\n" );
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document.write( "30 = 20/ total time <BR>\n" );
document.write( "Let return time be x \r<BR>\n" );
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document.write( "30 = 20/(0.5+x)<BR>\n" );
document.write( "30(0.5+x) = 20\r<BR>\n" );
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document.write( "15+30x = 20<BR>\n" );
document.write( "30x =5<BR>\n" );
document.write( "x= 5/30 = 1/6 hour\r<BR>\n" );
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document.write( "Time B to A is 1/6 <BR>\n" );
document.write( "Distance /time = speed\r<BR>\n" );
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document.write( "10/ (1/6) =60 km/h should be the return speed to get  average of total travel <BR>\n" );
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