document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1074235>Question 1074235</A>: <I><SPAN STYLE=\"word-break: break-all;\"> During a race on a circular track, a racecar burns fuel at a constant rate. After lap 4, the racecar has 22 gallons left in its tank. After lap 7, the racecar has 18 gallons left in its tank. Assuming the racecar does not refuel, after which lap will the racecar have 6 gallons left in its tank? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #688966 by </B><A HREF=/tutors/aboutme.mpl?userid=ankor@dixie-net.com><B>ankor@dixie-net.com(22740)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=ankor@dixie-net.com><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=ankor@dixie-net.com><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=688966\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> During a race on a circular track, a racecar burns fuel at a constant rate.<BR>\n" );
document.write( " After lap 4, the racecar has 22 gallons left in its tank. After lap 7, the racecar has 18 gallons left in its tank.<BR>\n" );
document.write( " Assuming the racecar does not refuel, after which lap will the racecar have 6 gallons left in its tank?<BR>\n" );
document.write( ":<BR>\n" );
document.write( "We can write a linear equation y = mx + b<BR>\n" );
document.write( "where x = lap number and y = amt of fuel left<BR>\n" );
document.write( "then<BR>\n" );
document.write( "x1 = 4; y1 = 22<BR>\n" );
document.write( "x2 = 7; y2 = 18<BR>\n" );
document.write( "use the slope formula: m = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%28y2+-+y1%29%2F%28x2+-+x1%29+ ALIGN=MIDDLE  ALT=\"%28y2+-+y1%29%2F%28x2+-+x1%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" >, we have<BR>\n" );
document.write( "m = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%2818+-+22%29%2F%287+-+4%29+ ALIGN=MIDDLE  ALT=\"%2818+-+22%29%2F%287+-+4%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" > = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=-4%2F3 ALIGN=MIDDLE  ALT=\"-4%2F3\"   DISABLED_style= \"max-width:90%; height:auto;\" > is the slope<BR>\n" );
document.write( ":<BR>\n" );
document.write( "Find the equation using the point/slope formula: y - y1 = m(x - x1)<BR>\n" );
document.write( "y - 22 = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=-4%2F3 ALIGN=MIDDLE  ALT=\"-4%2F3\"   DISABLED_style= \"max-width:90%; height:auto;\" >(x - 4)<BR>\n" );
document.write( "y = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=-4%2F3 ALIGN=MIDDLE  ALT=\"-4%2F3\"   DISABLED_style= \"max-width:90%; height:auto;\" >x + <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=16%2F3 ALIGN=MIDDLE  ALT=\"16%2F3\"   DISABLED_style= \"max-width:90%; height:auto;\" > + 22<BR>\n" );
document.write( "y = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=-4%2F3 ALIGN=MIDDLE  ALT=\"-4%2F3\"   DISABLED_style= \"max-width:90%; height:auto;\" >x + <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=16%2F3 ALIGN=MIDDLE  ALT=\"16%2F3\"   DISABLED_style= \"max-width:90%; height:auto;\" > + <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=66%2F3 ALIGN=MIDDLE  ALT=\"66%2F3\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "y = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=-4%2F3 ALIGN=MIDDLE  ALT=\"-4%2F3\"   DISABLED_style= \"max-width:90%; height:auto;\" >x + <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=82%2F3 ALIGN=MIDDLE  ALT=\"82%2F3\"   DISABLED_style= \"max-width:90%; height:auto;\" > is the equation<BR>\n" );
document.write( ":<BR>\n" );
document.write( "\"after which lap will the racecar have 6 gallons left in its tank?}<BR>\n" );
document.write( "y = 6<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=-4%2F3 ALIGN=MIDDLE  ALT=\"-4%2F3\"   DISABLED_style= \"max-width:90%; height:auto;\" >x + <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=82%2F3 ALIGN=MIDDLE  ALT=\"82%2F3\"   DISABLED_style= \"max-width:90%; height:auto;\" > = 6<BR>\n" );
document.write( "multiply equation by 3 to get rid of the denominators<BR>\n" );
document.write( "-4x + 82 = 3(6)<BR>\n" );
document.write( "-4x = 18 - 82<BR>\n" );
document.write( "-4x = -64<BR>\n" );
document.write( "x = -64/-4<BR>\n" );
document.write( "x = 16 is lap where he will 6 gal left\r<BR>\n" );
document.write( "\n" );
document.write( "   </SPAN>\n" );
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