document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=988251>Question 988251</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A circular magnet has an inner radius of r-cm, an outer radius 2cm larger and its depth is the same as the inner radius. If the total volume of the magnet is 120 mulitplied by pi cm^3, find r.<BR>\n" );
document.write( "I have written the equation, but cannot solve it.<BR>\n" );
document.write( "V= pi x (r+2)^2 x r - pi x r^2 x r </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #608989 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=608989\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> A circular magnet has an inner radius of r-cm, an outer radius 2cm larger and its depth is the same as the inner radius. If the total volume of the magnet is 120 mulitplied by pi cm^3, find r.<BR>\n" );
document.write( "I have written the equation, but cannot solve it.<BR>\n" );
document.write( "V= pi x (r+2)^2 x r - pi x r^2 x r <BR>\n" );
document.write( "just make equal to 120pi<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%28pi%2A%28r%2B2%29%5E2%2Ar%29+-+%28pi%2Ar%5E2%2Ar%29+=+120%2Api ALIGN=MIDDLE  ALT=\"%28pi%2A%28r%2B2%29%5E2%2Ar%29+-+%28pi%2Ar%5E2%2Ar%29+=+120%2Api\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "divide thru by pi, multiply r<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%28r%28r%2B2%29%5E2%29+-+r%5E3+=+120 ALIGN=MIDDLE  ALT=\"%28r%28r%2B2%29%5E2%29+-+r%5E3+=+120\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "FOIL (r+2)(r+2)<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%28r%5E2+%2B+4r+%2B+4%29+-+r%5E3+=+120 ALIGN=MIDDLE  ALT=\"r%28r%5E2+%2B+4r+%2B+4%29+-+r%5E3+=+120\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5E3%2B+4r%5E2+%2B+4r+-+r%5E3+=+120 ALIGN=MIDDLE  ALT=\"r%5E3%2B+4r%5E2+%2B+4r+-+r%5E3+=+120\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "r^3 cancel so we have<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=4r%5E2+%2B+4r+=+120 ALIGN=MIDDLE  ALT=\"4r%5E2+%2B+4r+=+120\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "Simplify, divide by 4<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5E2+%2B+r+=+30 ALIGN=MIDDLE  ALT=\"r%5E2+%2B+r+=+30\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "A quadratic equation<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=r%5E2+%2B+r+-+30+=+0 ALIGN=MIDDLE  ALT=\"r%5E2+%2B+r+-+30+=+0\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "factors to<BR>\n" );
document.write( "(r+6)(r-5) = 0<BR>\n" );
document.write( "positive solution<BR>\n" );
document.write( "r = 5<BR>\n" );
document.write( ":<BR>\n" );
document.write( "Did this make sense to you?  </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );