document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=285655>Question 285655</A>: <I><SPAN STYLE=\"word-break: break-all;\"> 	Jen’s boat cruised 45 miles upstream and 45 miles back in a total of 8 hr.  The speed of the river is 3 mph.  Find the speed of the boat in still water.\r<BR>\n" );
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document.write( "I need help with this word problem.\r<BR>\n" );
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document.write( "Thank you.<BR>\n" );
document.write( "Cynthia </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #207089 by </B><A HREF=/tutors/aboutme.mpl?userid=stanbon><B>stanbon(75887)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=stanbon><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=207089\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Jen’s boat cruised 45 miles upstream and 45 miles back in a total of 8 hr. The speed of the river is 3 mph. Find the speed of the boat in still water. <BR>\n" );
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document.write( "Upstream DATA:<BR>\n" );
document.write( "distance = 45 miles ; rate = b-3 mph ; time = d/r = 45/(b-3) hrs.<BR>\n" );
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document.write( "Downstream  DATA:<BR>\n" );
document.write( "distance = 45 miles ; rate = b+3 mph ; time = d/r = 45/(b+3) hrs<BR>\n" );
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document.write( "Equation:<BR>\n" );
document.write( "time + time = 8 hr<BR>\n" );
document.write( "45/(b-3) + 45/(b+3) = 8<BR>\n" );
document.write( "Multiply thru by (b^2-9) to get:<BR>\n" );
document.write( "45(b+3) + 45(b-3) = 8(b^2-9)<BR>\n" );
document.write( "90b = 8b^2 - 72<BR>\n" );
document.write( "Rearrange:<BR>\n" );
document.write( "8b^2 - 90b - 72 = 0<BR>\n" );
document.write( "4b^2 -45b - 36 = 0<BR>\n" );
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document.write( "(b-12)(4b+3) = 0<BR>\n" );
document.write( "Positive solution:<BR>\n" );
document.write( "b = 12 mph (boat speed in still water)<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
document.write( "======================================= </SPAN>\n" );
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