document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=814097>Question 814097</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A candle is 8 in. tall after burning 2 hrs.  After 4 hrs it is 5 1/2 in. tall.  Write a linear equation to model the height y of the candle after x hours.  After how many hours will the candle be 4 inches tall? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #490098 by </B><A HREF=/tutors/aboutme.mpl?userid=josgarithmetic><B>josgarithmetic(39618)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=josgarithmetic><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=490098\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> The description gives two data points, (x,y) where x is time and y is tallness of the candle.  These two points are (2, 8) and (4, 5.5).  These two points define a line in variables x and y.\r<BR>\n" );
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document.write( "That desired line:<BR>\n" );
document.write( "All using slope-intercept form, <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=m=%285.5-8%29%2F%284-2%29=-2.5%2F2=-5%2F4 ALIGN=MIDDLE  ALT=\"m=%285.5-8%29%2F%284-2%29=-2.5%2F2=-5%2F4\"   DISABLED_style= \"max-width:90%; height:auto;\" >;<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=y=mx%2Bb ALIGN=MIDDLE  ALT=\"y=mx%2Bb\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=b=y-mx ALIGN=MIDDLE  ALT=\"b=y-mx\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "Use either point from the problem description,<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=b=8-%28-5%2F4%29%2A2 ALIGN=MIDDLE  ALT=\"b=8-%28-5%2F4%29%2A2\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=b=8%2B%285%2F4%29%2A2 ALIGN=MIDDLE  ALT=\"b=8%2B%285%2F4%29%2A2\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=b=8%2B5%2F2=8%2B2.5 ALIGN=MIDDLE  ALT=\"b=8%2B5%2F2=8%2B2.5\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=b=10.5 ALIGN=MIDDLE  ALT=\"b=10.5\"   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
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document.write( "The equation for the line is <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=highlight%28y=%285%2F4%29x%2B10%261%2F2%29 ALIGN=MIDDLE  ALT=\"highlight%28y=%285%2F4%29x%2B10%261%2F2%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >;<BR>\n" );
document.write( "Again, y is tallness or height of the candle in inches, and x is time in hours after burning (at the wick).  The question is about how much time to burn to become 4.5 inches.  JUST SOLVE THE EQUATION FOR x, and let y=4.5.\r<BR>\n" );
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document.write( "The whole situation could have been analyzed using x for tallness and y for burn time, but normally, most people would use time as an independant variable and something else as the dependant variable. </SPAN>\n" );
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