document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1132693>Question 1132693</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Meg rowed her boat upstream at a distance of 48 mi. then rowed back to the starting point. The total time of the trip was 16 hours. If the rate of the current was 4mph,  find the average speed of the boat relative to the water </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #749833 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=749833\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> <br><BR>\n" );
document.write( "The formal algebraic solution by tutor @ikleyn is fine, and well presented.<br><BR>\n" );
document.write( "However, with the information given, this problem can be solved mentally with a bit of trial and error.<br><BR>\n" );
document.write( "Since the rate of the current is 4mph, the difference between the upstream and downstream speeds will be 8mph.<br><BR>\n" );
document.write( "Then, since the total time for the trip was EXACTLY 16 hours, the speed of the boat in still water will almost certainly be a whole number; and then the times for the upstream and downstream trips will be whole numbers.<br><BR>\n" );
document.write( "A very small bit of mental arithmetic finds that two speeds (mph) that differ by 8 and are factors of 48 (miles) are 4 and 12.<br><BR>\n" );
document.write( "And indeed these speeds work with the given information -- the total time for the trip is 48/4+48/12 = 12+4 = 16 hours.<br><BR>\n" );
document.write( "So the upstream and downstream rates are 4mph and 12mph; since the rate of the current is 4mph, the rate of the boat in still water is 8mph. </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );