document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1125804>Question 1125804</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Deandre bought a desktop computer and a laptop computer. Before finance charges, the laptop cost <BR>\n" );
document.write( "$300 more than the desktop. He paid for the computers using two different financing plans. For the desktop the interest rate was 9% per year, and for the laptop it was 7% per year. The total finance charges for one year were $365. How much did each computer cost before finance charges?  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #742157 by </B><A HREF=/tutors/aboutme.mpl?userid=kasperk><B>kasperk(4)</B></A><img src=\"/images/stars/iconNewId_16x16.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=kasperk><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=742157\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Let $D = cost of the desktop<BR>\n" );
document.write( "Then $D + $300 = cost of the laptop<BR>\n" );
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document.write( "DESKtop computer:<BR>\n" );
document.write( "Principal amount = D<BR>\n" );
document.write( "r = 9% = .09<BR>\n" );
document.write( "t = 1 year<BR>\n" );
document.write( "Therefore, using a simple interest formula I = Prt, we find I = D·(0.09)·1 = 0.09D<BR>\n" );
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document.write( "LAPtop computer:<BR>\n" );
document.write( "Principal amount = D+300<BR>\n" );
document.write( "r = 7% = .07<BR>\n" );
document.write( "t = 1 year<BR>\n" );
document.write( "Therefore, I = Prt = (D+300)·(0.07)·1 = 0.07(D+300) = 0.07D + 21\r<BR>\n" );
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document.write( "If we add up the interest on the desktop and the interest on the laptop, that total interest should equal $365 (interestingly, $1 per day of the year!):<BR>\n" );
document.write( "<br><BR>\n" );
document.write( "0.09D + 0.07D + 21 = 365<BR>\n" );
document.write( "Combine like terms:<BR>\n" );
document.write( "0.16D + 21 = 365<BR>\n" );
document.write( "Subtract 21 from each side of the equation:<BR>\n" );
document.write( "0.16D = 344<BR>\n" );
document.write( "Divide both sides of the equation by 0.16:<BR>\n" );
document.write( "D = $2150 = desktop computer cost<BR>\n" );
document.write( "D + 300 = $2450 = laptop computer cost </SPAN>\n" );
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