document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=138079>Question 138079</A>This question is from textbook <A HREF=http://www.amazon.com/exec/obidos/ASIN/0130442631/algebrahomeworkh>Prentice Hall Algebra 1</A><BR>\n" );
document.write( ": <I><SPAN STYLE=\"word-break: break-all;\"> I would very much appreciate if you could answer this question I do not know what category this is:\r<BR>\n" );
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document.write( "The speed of a boat in still water is 10km/h. The boat travels 12km upstream and 28km downstream in a total time of 4 hours. What is the speed of the stream?\r<BR>\n" );
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document.write( "Thank You </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #100859 by </B><A HREF=/tutors/aboutme.mpl?userid=ankor@dixie-net.com><B>ankor@dixie-net.com(22740)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=ankor@dixie-net.com><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=ankor@dixie-net.com><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=100859\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> The speed of a boat in still water is 10km/h. The boat travels 12km upstream and 28km downstream in a total time of 4 hours. What is the speed of the stream? <BR>\n" );
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document.write( "Let x = speed of the current:<BR>\n" );
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document.write( "(10-x) = speed upstream<BR>\n" );
document.write( "and<BR>\n" );
document.write( "(10-x) = speed downstream<BR>\n" );
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document.write( "Write a time equation: Time = Dist/speed<BR>\n" );
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document.write( "Upstream time + downstream time = 4 hrs<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=12%2F%28%2810-x%29%29 ALIGN=MIDDLE  ALT=\"12%2F%28%2810-x%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > + <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=28%2F%28%2810%2Bx%29%29 ALIGN=MIDDLE  ALT=\"28%2F%28%2810%2Bx%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > = 4<BR>\n" );
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document.write( "Multiply equation by (10-x)(10+x), get rid of the denominator, you have:<BR>\n" );
document.write( "12(10+x) + 28(10-x) = 4(10-x)(10+x)<BR>\n" );
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document.write( "120 + 12x + 280 - 28x = 4(100 - x^2)<BR>\n" );
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document.write( "-16x + 400 = 400 - 4x^2<BR>\n" );
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document.write( "+4x^2 - 16x + 400 - 400 = 0<BR>\n" );
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document.write( "4x^2 - 16x = 0<BR>\n" );
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document.write( "4x(x - 4) = 0<BR>\n" );
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document.write( "x = +4 km/h is the speed of the current<BR>\n" );
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document.write( "Check solution by finding the times (Speed up = 6 km/h; Speed down = 14 km/h):<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=12%2F6 ALIGN=MIDDLE  ALT=\"12%2F6\"   DISABLED_style= \"max-width:90%; height:auto;\" > + <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=28%2F14 ALIGN=MIDDLE  ALT=\"28%2F14\"   DISABLED_style= \"max-width:90%; height:auto;\" > = 4 hrs<BR>\n" );
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