document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=346655>Question 346655</A>: <I><SPAN STYLE=\"word-break: break-all;\"> If you save 10$ one month, 12$ the next month, 14$ the next month, and so on, how long will you take to save a total of 400$?<BR>\n" );
document.write( "How would you make this into a formula? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #247925 by </B><A HREF=/tutors/aboutme.mpl?userid=jrfrunner><B>jrfrunner(365)</B></A><img src=\"/images/stars/stars-10.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=jrfrunner><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=jrfrunner><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=247925\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> you are looking for summing an arithmetic series<BR>\n" );
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document.write( "the sequence is 10,12,14,.....    such that is sum =400<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=a%5Bi%5D=a%5B0%5D%2B%28i-1%29%2Adelta ALIGN=MIDDLE  ALT=\"a%5Bi%5D=a%5B0%5D%2B%28i-1%29%2Adelta\"   DISABLED_style= \"max-width:90%; height:auto;\" > where <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=delta ALIGN=MIDDLE  ALT=\"delta\"   DISABLED_style= \"max-width:90%; height:auto;\" > is the difference between to consecutive sequence numbers,  in this case <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=a%5B0%5D=10 ALIGN=MIDDLE  ALT=\"a%5B0%5D=10\"   DISABLED_style= \"max-width:90%; height:auto;\" > and <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=delta=2 ALIGN=MIDDLE  ALT=\"delta=2\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=a%5Bi%5D=10%2B%28i-1%29%2A2 ALIGN=MIDDLE  ALT=\"a%5Bi%5D=10%2B%28i-1%29%2A2\"   DISABLED_style= \"max-width:90%; height:auto;\" >=<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=8%2B2i ALIGN=MIDDLE  ALT=\"8%2B2i\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=sum%28a%5Bi%5D%29 ALIGN=MIDDLE  ALT=\"sum%28a%5Bi%5D%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >from 1 to n =<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=sum%28%288%2B2i%29%29 ALIGN=MIDDLE  ALT=\"sum%28%288%2B2i%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >= <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=sum%288%29%2B2%2Asum%28i%29 ALIGN=MIDDLE  ALT=\"sum%288%29%2B2%2Asum%28i%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >=<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=8n+%2B+2%2A%28n%2A%28n%2B1%29%2F2%29 ALIGN=MIDDLE  ALT=\"8n+%2B+2%2A%28n%2A%28n%2B1%29%2F2%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >=<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=8n%2Bn%2A%28n%2B1%29 ALIGN=MIDDLE  ALT=\"8n%2Bn%2A%28n%2B1%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >=<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=8n%2Bn%5E2%2Bn=n%5E2%2B9n ALIGN=MIDDLE  ALT=\"8n%2Bn%5E2%2Bn=n%5E2%2B9n\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
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document.write( "since we want to know when this sum=400\r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=400=n%5E2%2B9n ALIGN=MIDDLE  ALT=\"400=n%5E2%2B9n\"   DISABLED_style= \"max-width:90%; height:auto;\" >--> <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=0=n%5E2%2B9n-400 ALIGN=MIDDLE  ALT=\"0=n%5E2%2B9n-400\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
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document.write( "solve for n using quadratic formula<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+n=%28-9%2B-sqrt%2881-4%2A%28-400%29%29%29%2F2 ALIGN=MIDDLE  ALT=\"+n=%28-9%2B-sqrt%2881-4%2A%28-400%29%29%29%2F2\"   DISABLED_style= \"max-width:90%; height:auto;\" > <BR>\n" );
document.write( "n=-25 or n=16, since we want the number of months, we take the positive answer<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=highlight%28n=16+months%29 ALIGN=MIDDLE  ALT=\"highlight%28n=16+months%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > </SPAN>\n" );
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