document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=515488>Question 515488</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A boat can go 20 km downstream in 2 hours. The return trip takes 5 hours. What would the speed of the boat be if there was no current? What is 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 #344003 by </B><A HREF=/tutors/aboutme.mpl?userid=oberobic><B>oberobic(2304)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=oberobic><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=344003\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> d = r*t is the basic distance equation.<BR>\n" );
document.write( ".<BR>\n" );
document.write( "d = 20km<BR>\n" );
document.write( ".<BR>\n" );
document.write( "s = speed of the boat in calm water<BR>\n" );
document.write( "c = speed of the current<BR>\n" );
document.write( "so<BR>\n" );
document.write( "r = s-c going upstream (against the current)<BR>\n" );
document.write( "r = s+c going down stream (with the current)<BR>\n" );
document.write( ".<BR>\n" );
document.write( "Going downstream...<BR>\n" );
document.write( "d/r = 2 hr<BR>\n" );
document.write( "d/(s+c) = 2 <BR>\n" );
document.write( "20 = 2(s+c)<BR>\n" );
document.write( "2(s+c) = 20<BR>\n" );
document.write( "s+c = 10<BR>\n" );
document.write( ".<BR>\n" );
document.write( "Going upstream<BR>\n" );
document.write( "d/r = 5 hr<BR>\n" );
document.write( "d/(s-c) = 5<BR>\n" );
document.write( "20 = 5(s-c)<BR>\n" );
document.write( "5(s-c) = 20<BR>\n" );
document.write( "s-c = 4<BR>\n" );
document.write( ".<BR>\n" );
document.write( "s + c = 10<BR>\n" );
document.write( "s - c = 4<BR>\n" );
document.write( "----------<BR>\n" );
document.write( "2s = 14<BR>\n" );
document.write( "s = 7 km/h<BR>\n" );
document.write( ".<BR>\n" );
document.write( "c  = 10-s<BR>\n" );
document.write( "c = 3 km/h<BR>\n" );
document.write( ".<BR>\n" );
document.write( "Check the distances<BR>\n" );
document.write( ".<BR>\n" );
document.write( "2 * (7+3) = 20 km<BR>\n" );
document.write( "5 * (7-3) = 20 km<BR>\n" );
document.write( ".<BR>\n" );
document.write( "Answer:  The boat can achieve 7 km/h in still water; the current is 3 km/h.<BR>\n" );
document.write( ".<BR>\n" );
document.write( "Done. </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );