document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1126950>Question 1126950</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Jeff starts driving at 65 miles per hour from the<BR>\n" );
document.write( "same point that Lauren starts driving at 70<BR>\n" );
document.write( "miles per hour. They drive in opposite<BR>\n" );
document.write( "directions, and Lauren has a half-hour head<BR>\n" );
document.write( "start. How long will they be able to talk on<BR>\n" );
document.write( "their cell phones that have a 250-mile range? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #743363 by </B><A HREF=/tutors/aboutme.mpl?userid=Theo><B>Theo(13342)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Theo><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=Theo><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=743363\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> i think it works this way.\r<BR>\n" );
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document.write( "jeff drives at 65 miles per hour from the same point that lauren drives at 65 miles per hour.\r<BR>\n" );
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document.write( "they drive in opposite directions.\r<BR>\n" );
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document.write( "lauren has a half hour head starts.\r<BR>\n" );
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document.write( "rate * time = distance.\r<BR>\n" );
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document.write( "for jeff, the equation becomes 65 * T = D\r<BR>\n" );
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document.write( "T is the time<BR>\n" );
document.write( "D is the distance.\r<BR>\n" );
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document.write( "for lauren, the equation becomes 70 * (T + .5) = 250 - D\r<BR>\n" );
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document.write( "T + 5 means she drives a half hour more than jeff.\r<BR>\n" );
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document.write( "since they drive in opposite directions, the distance that each travels is additive.\r<BR>\n" );
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document.write( "you get D + 250 - D = 250.\r<BR>\n" );
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document.write( "250 is the total distance both travel.\r<BR>\n" );
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document.write( "since D = 65 * T and 250 - D = 70 * (T + .5), then you get:\r<BR>\n" );
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document.write( "65 * T + 70 * (T + .5) = 250\r<BR>\n" );
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document.write( "simplify to get 65 * T + 70 * T + 35 = 250\r<BR>\n" );
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document.write( "combine like terms to 135 * T + 35 = 250\r<BR>\n" );
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document.write( "subtract 35 from both sides of the equation to get 135 * T = 215\r<BR>\n" );
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document.write( "divide both side of the equation by 135 to get T = 215 / 135 = 1.592592593.\r<BR>\n" );
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document.write( "jeff traveled 65 miles per hour * that for a distance of 103.5185185 miles.\r<BR>\n" );
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document.write( "lauren traveled 70 miles per hour * (that + .5) for a distance of 146.4814815 miles.\r<BR>\n" );
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document.write( "add the miles up and they total 250 miles.\r<BR>\n" );
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document.write( "jeff traveled for 1.592592593 hours at 65 miles per hour.\r<BR>\n" );
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document.write( "lauren traveled for 1.592592593 + .5 = 2.092592593 hours at 70 miles per hour.\r<BR>\n" );
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document.write( "the questions was:\r<BR>\n" );
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document.write( "How long will they be able to talk on their cell phones that have a 250-mile range?\r<BR>\n" );
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document.write( "if you are talking about how long they can talk to each other on their cell phone after lauren starts driving, then that has to be 2.092592593 hours.\r<BR>\n" );
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document.write( "after that amount of time, their cell phones will be out of range of each other.\r<BR>\n" );
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