document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=214899>Question 214899</A>: <I><SPAN STYLE=\"word-break: break-all;\"> This question I come up with the wrong answer:<BR>\n" );
document.write( "Pete drove from Buffalo to Boston, a distance of 720km. On return trip he increased his speed by 10km/h.  If the total trip took 17h, what was his speed from Boston to Buffalo?\r<BR>\n" );
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document.write( "I'm having trouble working it out, I begin with this:\r<BR>\n" );
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document.write( "I start with (720/x)+(720/x+10)\r<BR>\n" );
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document.write( "Expanded it to: 17x^2 - 1270x + 7200\r<BR>\n" );
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document.write( "Speed I got next using the quadratic equation: 62.5\r<BR>\n" );
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document.write( "But thats apparently wrong, what am I doing wrong? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #162351 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=162351\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Pete drove from Buffalo to Boston, a distance of 720km. On return trip he increased his speed by 10km/h. If the total trip took 17h, what was his speed from Boston to Buffalo? <BR>\n" );
document.write( "I'm having trouble working it out, I begin with this: <BR>\n" );
document.write( "I start with (720/x)+(720/x+10) <BR>\n" );
document.write( "Expanded it to: 17x^2 - 1270x + 7200 <BR>\n" );
document.write( "Speed I got next using the quadratic equation: 62.5 <BR>\n" );
document.write( "But thats apparently wrong, what am I doing wrong?<BR>\n" );
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document.write( "Buff to Bost DATA:<BR>\n" );
document.write( "distance = 720 km ; rate = x km/h ; time = d/r = 720/x hrs<BR>\n" );
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document.write( "Bost to Buff DATA:<BR>\n" );
document.write( "distance = 720 km ; rate = x+10 km/h ; time = 720/(x+10) hrs<BR>\n" );
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document.write( "Equation:<BR>\n" );
document.write( "time + time = 17 hrs.<BR>\n" );
document.write( "(720/x) + (720/(x+10)) = 17<BR>\n" );
document.write( "Multiply thru by x(x+10) to get:<BR>\n" );
document.write( "720(x+10) + 720(x) = 17x(x+10)<BR>\n" );
document.write( "720x + 7200 + 720x = 17x^2 + 170x<BR>\n" );
document.write( "17x^2 - 1270x - 7200 = 0<BR>\n" );
document.write( "(x-80)(17x + 90) = 0<BR>\n" );
document.write( "Positive solution:<BR>\n" );
document.write( "x+ 10 = 90 km/h (rate from Boston to Buffalo)<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H. </SPAN>\n" );
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