document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1208940>Question 1208940</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A motorboat can maintain a constant speed of 16 miles per hour relative to the water. The boat makes a trip upstream to a certain point 20 minutes; the return trip take 15 minutes. What is the speed of the current? \r<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 #847493 by </B><A HREF=/tutors/aboutme.mpl?userid=greenestamps><B>greenestamps(13200)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=greenestamps><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=greenestamps><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=847493\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> <br><BR>\n" );
document.write( "The solution method  from the other tutor is fine, and it is probably what you will find in most references.<br><BR>\n" );
document.write( "Usually, when the distances are the same at two different speeds, the algebra required to find the answer is easier if you use the fact that the speed is inversely proportional to the time.  A solution using that starting point is shown below.<br><BR>\n" );
document.write( "Let x be the speed of the current.  Then the upstream speed is 16-x and the downstream speed is 16+x.<br><BR>\n" );
document.write( "The distances upstream and downstream are the same.  Then, since the ratio of times upstream and downstream is 20:15 = 4:3, the ratio of the upstream and downstream speeds is 3:4.  So<br><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%2816-x%29%2F%2816%2Bx%29=3%2F4 ALIGN=MIDDLE  ALT=\"%2816-x%29%2F%2816%2Bx%29=3%2F4\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3%2816%2Bx%29=4%2816-x%29 ALIGN=MIDDLE  ALT=\"3%2816%2Bx%29=4%2816-x%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=48%2B3x=64-4x ALIGN=MIDDLE  ALT=\"48%2B3x=64-4x\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=7x=16 ALIGN=MIDDLE  ALT=\"7x=16\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=x=16%2F7 ALIGN=MIDDLE  ALT=\"x=16%2F7\"   DISABLED_style= \"max-width:90%; height:auto;\" ><br><BR>\n" );
document.write( "ANSWER: 16/7 mph, or 2 2/7 mph<br><BR>\n" );
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