document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=103605>Question 103605</A>This question is from textbook <A HREF=http://www.amazon.com/exec/obidos/ASIN/0030416477/algebrahomeworkh>Precalculus</A><BR>\n" );
document.write( ": <I><SPAN STYLE=\"word-break: break-all;\"> To get to work Sam jogs 3 kilometers to the train, then rides the remaining 5 kilometers.  If the train goes 40 km  per hour faster than Sam's constant rate of jogging and the entire trip takes 1/2 hour how fast does Sam jog? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #75408 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=75408\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> To get to work Sam jogs 3 kilometers to the train, then rides the remaining 5 kilometers. If the train goes 40 km per hour faster than Sam's constant rate of jogging and the entire trip takes 1/2 hour how fast does Sam jog?<BR>\n" );
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document.write( "Let s = his jogging speed<BR>\n" );
document.write( "then<BR>\n" );
document.write( "(s+40) = train speed<BR>\n" );
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document.write( "Write a time equation: Time = Distance/speed<BR>\n" );
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document.write( "jog time + train time = .5 hrs<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3%2Fs ALIGN=MIDDLE  ALT=\"3%2Fs\"   DISABLED_style= \"max-width:90%; height:auto;\" > + <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=5%2F%28%28s%2B40%29%29 ALIGN=MIDDLE  ALT=\"5%2F%28%28s%2B40%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > = .5<BR>\n" );
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document.write( "Multiply equation by s(s+40) and you have:<BR>\n" );
document.write( "3(s+40) + 5s = .5(s(s+40))<BR>\n" );
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document.write( "3s + 120 + 5s = .5s^2 + 20s<BR>\n" );
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document.write( "8s + 120 = .5s^2 + 20s<BR>\n" );
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document.write( "0 = .5s^2 + 20s - 8s - 120<BR>\n" );
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document.write( ".5s^2 + 12s - 120 = 0; a quadratic equation<BR>\n" );
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document.write( "Use the quadratic formula to find s: a=.5; b=12; c=-120<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+ ALIGN=MIDDLE  ALT=\"x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=s+=+%28-12+%2B-+sqrt%28+12%5E2+-+4+%2A+.5+%2A+-120%29%29%2F%282%2A.5%29+ ALIGN=MIDDLE  ALT=\"s+=+%28-12+%2B-+sqrt%28+12%5E2+-+4+%2A+.5+%2A+-120%29%29%2F%282%2A.5%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=s+=+%28-12+%2B-+sqrt%28144+-+%28-240%29+%29%29%2F%281%29+ ALIGN=MIDDLE  ALT=\"s+=+%28-12+%2B-+sqrt%28144+-+%28-240%29+%29%29%2F%281%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=s+=+%28-12+%2B-+sqrt%28144+%2B+240+%29%29+ ALIGN=MIDDLE  ALT=\"s+=+%28-12+%2B-+sqrt%28144+%2B+240+%29%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=s+=+-12+%2B-+sqrt%28384+%29+ ALIGN=MIDDLE  ALT=\"s+=+-12+%2B-+sqrt%28384+%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
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document.write( "s = -12 + 19.5959; we only need the positive solution here<BR>\n" );
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document.write( "s = +7.5959 km/hr is his jogging speed<BR>\n" );
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document.write( "Check solution by finding the time<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3%2F7.6 ALIGN=MIDDLE  ALT=\"3%2F7.6\"   DISABLED_style= \"max-width:90%; height:auto;\" > + <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=5%2F47.6 ALIGN=MIDDLE  ALT=\"5%2F47.6\"   DISABLED_style= \"max-width:90%; height:auto;\" > =<BR>\n" );
document.write( "   .394 + .105  = .499 ~ .5 hrs<BR>\n" );
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document.write( "Did this make sense to you? Any questions? </SPAN>\n" );
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