document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=124538>Question 124538</A>This question is from textbook <A HREF=http://www.amazon.com/exec/obidos/ASIN/0534417957/algebrahomeworkh></A><BR>\n" );
document.write( ": <I><SPAN STYLE=\"word-break: break-all;\"> A person can drive from town A to town B at a certain rate of speed in 6 hours. If he increases his speed by 20kph he can make the trip in four hours. How far is it from town A to B. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #91275 by </B><A HREF=/tutors/aboutme.mpl?userid=Earlsdon><B>Earlsdon(6294)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Earlsdon><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/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=91275\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Use the distance formula on this problem:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d+=+rt ALIGN=MIDDLE  ALT=\"d+=+rt\"   DISABLED_style= \"max-width:90%; height:auto;\" > where:d = distance, r = rate(speed) and t = time of travel.<BR>\n" );
document.write( "For the first trip:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t%5B1%5D+=+6 ALIGN=MIDDLE  ALT=\"t%5B1%5D+=+6\"   DISABLED_style= \"max-width:90%; height:auto;\" > and we don't know <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5B1%5D ALIGN=MIDDLE  ALT=\"r%5B1%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" > <BR>\n" );
document.write( "For the second trip:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t%5B2%5D+=+4 ALIGN=MIDDLE  ALT=\"t%5B2%5D+=+4\"   DISABLED_style= \"max-width:90%; height:auto;\" > and <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5B2%5D+=+r%5B1%5D%2B20 ALIGN=MIDDLE  ALT=\"r%5B2%5D+=+r%5B1%5D%2B20\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "and, of course, d is the same in both cases.<BR>\n" );
document.write( "So, we can write:<BR>\n" );
document.write( "1) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d+=+6r%5B1%5D ALIGN=MIDDLE  ALT=\"d+=+6r%5B1%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" > and...<BR>\n" );
document.write( "2) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d+=+4%28r%5B1%5D%2B20%29 ALIGN=MIDDLE  ALT=\"d+=+4%28r%5B1%5D%2B20%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > setting these two equal to each other and simplifying...<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=6r%5B1%5D+=+4r%5B1%5D%2B80 ALIGN=MIDDLE  ALT=\"6r%5B1%5D+=+4r%5B1%5D%2B80\"   DISABLED_style= \"max-width:90%; height:auto;\" > Subtract <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=4r%5B1%5D ALIGN=MIDDLE  ALT=\"4r%5B1%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" > from both sides.<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=2r%5B1%5D+=+80 ALIGN=MIDDLE  ALT=\"2r%5B1%5D+=+80\"   DISABLED_style= \"max-width:90%; height:auto;\" > Divide both sides by 2.<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5B1%5D+=+40 ALIGN=MIDDLE  ALT=\"r%5B1%5D+=+40\"   DISABLED_style= \"max-width:90%; height:auto;\" > Now we can find the distance, d.<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d+=+r%5B1%5Dt%5B1%5D ALIGN=MIDDLE  ALT=\"d+=+r%5B1%5Dt%5B1%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" > Substitute <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5B1%5D+=+40 ALIGN=MIDDLE  ALT=\"r%5B1%5D+=+40\"   DISABLED_style= \"max-width:90%; height:auto;\" >and<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t%5B1%5D+=+6 ALIGN=MIDDLE  ALT=\"t%5B1%5D+=+6\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d+=+40%2A6 ALIGN=MIDDLE  ALT=\"d+=+40%2A6\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d+=+240 ALIGN=MIDDLE  ALT=\"d+=+240\"   DISABLED_style= \"max-width:90%; height:auto;\" >km.<BR>\n" );
document.write( "Check: Substitute <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5B2%5D+=+r%5B1%5D%2B20 ALIGN=MIDDLE  ALT=\"r%5B2%5D+=+r%5B1%5D%2B20\"   DISABLED_style= \"max-width:90%; height:auto;\" > and <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t%5B2%5D+=+4 ALIGN=MIDDLE  ALT=\"t%5B2%5D+=+4\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d+=+r%5B2%5Dt%5B2%5D ALIGN=MIDDLE  ALT=\"d+=+r%5B2%5Dt%5B2%5D\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d+=+%2840%2B20%29%2A4 ALIGN=MIDDLE  ALT=\"d+=+%2840%2B20%29%2A4\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d+=+60%2A4 ALIGN=MIDDLE  ALT=\"d+=+60%2A4\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d+=+240 ALIGN=MIDDLE  ALT=\"d+=+240\"   DISABLED_style= \"max-width:90%; height:auto;\" >km.<BR>\n" );
document.write( "The distance from town A to town B is 240 km.\r<BR>\n" );
document.write( "\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );