document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=392239>Question 392239</A>: <I><SPAN STYLE=\"word-break: break-all;\"> It took 3 hours to row a boat 18 km against the current.  The return trip with the current took 1 1/2 (1.5) hours.  Find the speed of the rowboat in still water.\r<BR>\n" );
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document.write( "I already tried:<BR>\n" );
document.write( "d = 3(r-18)  d = 1.5(r+18)<BR>\n" );
document.write( "d = 3r - 54   d = 1.5r + 27<BR>\n" );
document.write( "3r - 54 = 1.5r + 27<BR>\n" );
document.write( "3r = 1.5 = 81<BR>\n" );
document.write( "1.5r = 81<BR>\n" );
document.write( "r = 54 km/hr\r<BR>\n" );
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document.write( "d = 3(54-18)<BR>\n" );
document.write( "d = 3(36)<BR>\n" );
document.write( "d = 108 km\r<BR>\n" );
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document.write( "d = 3*54-54<BR>\n" );
document.write( "d = 108 km\r<BR>\n" );
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document.write( "But the speed of the rowboat in still water can't be 54 km/hr, can it? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #278414 by </B><A HREF=/tutors/aboutme.mpl?userid=Alan3354><B>Alan3354(69443)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Alan3354><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=Alan3354><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=278414\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> 18/3 = 6 km/hr<BR>\n" );
document.write( "18/1.5 = 12 km/hr<BR>\n" );
document.write( "The boat's speed is the average = (6 + 12)/2 = 9 km/hr<BR>\n" );
document.write( "The current speed is the difference = 3 km/hr<BR>\n" );
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document.write( "I already tried:<BR>\n" );
document.write( "d = 3(r-18) d = 1.5(r+18)<BR>\n" );
document.write( "d = 3r - 54 d = 1.5r + 27<BR>\n" );
document.write( "------<BR>\n" );
document.write( "If you include units, you'll see that your approach is not right.<BR>\n" );
document.write( "d = 3(r-18) d = 1.5(r+18)<BR>\n" );
document.write( "r-18 --> km/hr - km  The units don't match, so something's wrong.  Using the units can help to avoid mistakes.<BR>\n" );
document.write( " </SPAN>\n" );
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