document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=154514>Question 154514</A>: <I><SPAN STYLE=\"word-break: break-all;\"> This one's killing me...\r<BR>\n" );
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document.write( "In 1980, there were about 168 million vehicles and about 233 million people in the United States. The number of vehicles has been growing at 4% a year, while the population has been growing at 1% a year. \r<BR>\n" );
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document.write( "(a) Write a formula for the number of vehicles as a function of years since 1980.\r<BR>\n" );
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document.write( "I came up with V(t)=168(1.4)^t; which seems to work out via calculator, but is incorrect.\r<BR>\n" );
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document.write( "I would greatly appreciate any help!!\r<BR>\n" );
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document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #113761 by </B><A HREF=/tutors/aboutme.mpl?userid=BrittanyM><B>BrittanyM(80)</B></A><img src=\"/images/stars/stars-08.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=BrittanyM><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=113761\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> I think I might have found a solution for you.\r<BR>\n" );
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document.write( "I'm not sure if you're familiar with PERT,  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=Pe%5Ert ALIGN=MIDDLE  ALT=\"Pe%5Ert\"   DISABLED_style= \"max-width:90%; height:auto;\" >  but it's a very useful model for computing population growth over time.  In this case, we can use it to model the growth of motor vehicles over time.\r<BR>\n" );
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document.write( "So for this little problem, I came up with\r<BR>\n" );
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document.write( "V(t) = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=168%28million%29e%5E%280.04t%29 ALIGN=MIDDLE  ALT=\"168%28million%29e%5E%280.04t%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
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document.write( "We set this up by knowing that in <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=Pe%5Ert ALIGN=MIDDLE  ALT=\"Pe%5Ert\"   DISABLED_style= \"max-width:90%; height:auto;\" >, P is the principle (or the population where time is zero), r is rate, and t is time.\r<BR>\n" );
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document.write( "If you choose values for time and plug this into your calculator, you shouold come up with pretty accurate answers.   </SPAN>\n" );
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