document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=25489>Question 25489</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The boat travels 35 km upstream and then back again in 4 h 48min. If the speed of the boat in still water is 15 km/h, 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 #13683 by </B><A HREF=/tutors/aboutme.mpl?userid=Paul><B>Paul(988)</B></A><img src=\"/images/stars/stars-11.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Paul><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=13683\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> <BR>\n" );
document.write( "48 min --->0.8h<BR>\n" );
document.write( "Speed of the boat with the water = x+15<BR>\n" );
document.write( "Speed of the boat against a water = x-15<BR>\n" );
document.write( "Total distance = 35<BR>\n" );
document.write( "Total time = 4.8h<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=35%2Fx-15%2B35%2Fx%2B15=4.8 ALIGN=MIDDLE  ALT=\"35%2Fx-15%2B35%2Fx%2B15=4.8\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "35[(x-15)-(x+15)]=4.8[(x-15)(x+15)]<BR>\n" );
document.write( "35(-30)=4.8(x^2-225)<BR>\n" );
document.write( "-1050=4.8x^2-1080<BR>\n" );
document.write( "4.8x^2-30=0<BR>\n" );
document.write( "4.8x^2=30<BR>\n" );
document.write( "x^2=6.25<BR>\n" );
document.write( "Square root it.<BR>\n" );
document.write( "x=2.5<BR>\n" );
document.write( "Hence the speed of the current is 2.5km/h.<BR>\n" );
document.write( "Paul. </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );