document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1204796>Question 1204796</A>: <I><SPAN STYLE=\"word-break: break-all;\"> In his​ motorboat, Tran travels upstream at top speed to his favorite fishing​ spot, a distance of 6 ​miles, in 2 hours.​ Returning, he finds that the trip​ downstream, still at top​ speed, takes only 1.5 hours. Find the speed of​ Tran's boat and the speed of the current.  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #841301 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=841301\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> <br><BR>\n" );
document.write( "Upstream, the rate is 6/2 = 3mph; downstream, it is 6/1.5 = 4mph.<br><BR>\n" );
document.write( "This \"upstream, downstream\" problem is a very common type of problem in which the sum of two numbers is A and the difference of those two numbers is B; in this problem those numbers are 4 and 3.<br><BR>\n" );
document.write( "If formal algebra is not required, this kind of problem is easily solved using logical reasoning.<br><BR>\n" );
document.write( "The boat speed, plus the current speed, is 4mph; the boat speed, minus the current speed, is 3mph.<br><BR>\n" );
document.write( "Picture those numbers on a number line.  When you start with the boat speed and add the current speed, the result is 4mph; when you start with the boat speed and subtract the current speed, the result is 3mph.<br><BR>\n" );
document.write( "Logic then tells you that the boat speed is halfway between 3mph and 4mph -- i.e., 3.5mph.  And then that means the current speed is 0.5mph.<br><BR>\n" );
document.write( "ANSWERS: Boat speed 3.5mph; current speed 0.5mph<br><BR>\n" );
document.write( "In general, for any problem like this...<br><BR>\n" );
document.write( "If A+B = m and A-B = n,<BR>\n" );
document.write( "Then A is halfway between m and n (i.e., the average of m and n) and B is the difference between that average and either of m or n.<br><BR>\n" );
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