document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=120930>Question 120930</A>: <I><SPAN STYLE=\"word-break: break-all;\"> I need help with this\r<BR>\n" );
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document.write( "Amy travels 450 miles at certain speed.  If the car had gone 15 mph faster, the trip would have taken 1 hour less.  I need to find amy's speed. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #88728 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=88728\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Amy travels 450 miles at certain speed. If the car had gone 15 mph faster, the trip would have taken 1 hour less. I need to find Amy's speed.<BR>\n" );
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document.write( "Let s = the \"certain speed\"<BR>\n" );
document.write( "Then<BR>\n" );
document.write( "(s+15) = \"If\" speed<BR>\n" );
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document.write( "Write a time equation: Time = Distance/speed<BR>\n" );
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document.write( "\"Certain speed\" time - 1 hr = \"If\" speed time<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=450%2Fs ALIGN=MIDDLE  ALT=\"450%2Fs\"   DISABLED_style= \"max-width:90%; height:auto;\" > - 1 = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=450%2F%28%28s%2B15%29%29 ALIGN=MIDDLE  ALT=\"450%2F%28%28s%2B15%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
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document.write( "Multiply equation by s(s+15) to get rid of the denominators<BR>\n" );
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document.write( "s(s+15)*<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=450%2Fs ALIGN=MIDDLE  ALT=\"450%2Fs\"   DISABLED_style= \"max-width:90%; height:auto;\" > - s(s+15)(1) = s(s+15)*<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=450%2F%28%28s%2B15%29%29 ALIGN=MIDDLE  ALT=\"450%2F%28%28s%2B15%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
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document.write( "Cancel out the denominators and you have:<BR>\n" );
document.write( "450(s+15) - (s^2 + 15s) = 450s<BR>\n" );
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document.write( "450s + 6750 - s^2 - 15s = 450s<BR>\n" );
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document.write( "-s^2 - 15s +450s - 450s + 6750 = 0; arrange as a quadratic equation<BR>\n" );
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document.write( "-s^2 - 15s + 6750 = 0<BR>\n" );
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document.write( "s^2 + 15s - 6750 = 0; multiplied by -1 (easier to factor)<BR>\n" );
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document.write( "Factors to <BR>\n" );
document.write( "(s+90)(s-75) = 0<BR>\n" );
document.write( "Positive solution:<BR>\n" );
document.write( "s = +75 mph is Amy's speed<BR>\n" );
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document.write( "Check solution by finding the time for each scenario<BR>\n" );
document.write( "450/75 = 6 hrs<BR>\n" );
document.write( "450/90 = 5 hrs<BR>\n" );
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document.write( "differs 1 hr; confirms our solution\r<BR>\n" );
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