document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=883415>Question 883415</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A laptop computer is purchased for $2700.  Each year its value decreases by 20%.  After how many years will the laptop first be worth under $900? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #533539 by </B><A HREF=/tutors/aboutme.mpl?userid=LinnW><B>LinnW(1048)</B></A><img src=\"/images/stars/stars-12.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=LinnW><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=LinnW><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=533539\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> (1 - % decrease)^x = 900<BR>\n" );
document.write( "where x is the number of years\r<BR>\n" );
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document.write( "2700*(0.80)^x = 900<BR>\n" );
document.write( "divide each side by 2700<BR>\n" );
document.write( "(0.80)^x = 900/2700<BR>\n" );
document.write( "(0.80)^x = 1/3\r<BR>\n" );
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document.write( "Take log of each side<BR>\n" );
document.write( "log((0.80)^x) = log(1/3)<BR>\n" );
document.write( "x*log(0.80) = log(1/3)<BR>\n" );
document.write( "divide each side by log(0.80)<BR>\n" );
document.write( "x = log(1/3)/log(0.80) = 4.923..<BR>\n" );
document.write( "Let's check 2700*(0.80)^4.923 = 900.69.. so we are close<BR>\n" );
document.write( "In just under 4.93 years we will have a value under $900 </SPAN>\n" );
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