document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=127641>Question 127641</A>This question is from textbook <A HREF=http://www.amazon.com/exec/obidos/ASIN/0534404693/algebrahomeworkh>algebra and trigonometry with analiytic geometry</A><BR>\n" );
document.write( ": <I><SPAN STYLE=\"word-break: break-all;\"> It has been estimated that 1000 curies of a radioactive substance introduced at a point on the surface of the open sea would spread over an area of 36000 km^2  in 40 days. Assuming that the area covered by the radioactive substance is a linear function of (t) time and is always circular in shape, express the radius (r) of the contamination as a function of (t).\r<BR>\n" );
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document.write( "please i need your help, i don't know how... </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #93618 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=93618\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> It has been estimated that 1000 curies of a radioactive substance introduced at a point on the surface of the open sea would spread over an area of 36000 km^2 in 40 days. Assuming that the area covered by the radioactive substance is a linear function of (t) time and is always circular in shape, express the radius (r) of the contamination as a function of (t). <BR>\n" );
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document.write( "Take the area of a circle equation; A = pi*r^2<BR>\n" );
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document.write( "we want to solve for r<BR>\n" );
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document.write( "pi*r^2 = A<BR>\n" );
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document.write( "r^2 = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=A%2Fpi ALIGN=MIDDLE  ALT=\"A%2Fpi\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
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document.write( "r = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=sqrt%28A%2Fpi%29 ALIGN=MIDDLE  ALT=\"sqrt%28A%2Fpi%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
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document.write( "Find the radius (km) after 40 days using the given area of 36000<BR>\n" );
document.write( "r = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=sqrt%2836000%2Fpi%29 ALIGN=MIDDLE  ALT=\"sqrt%2836000%2Fpi%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >}<BR>\n" );
document.write( "r = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=sqrt%2811459%29 ALIGN=MIDDLE  ALT=\"sqrt%2811459%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "r = 107 km<BR>\n" );
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document.write( "Find the slope using the coordinates of 0,0 (0 days, 0 radius) and 40, 107<BR>\n" );
document.write( "m = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=107%2F40 ALIGN=MIDDLE  ALT=\"107%2F40\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
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document.write( "r = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=107%2F40 ALIGN=MIDDLE  ALT=\"107%2F40\"   DISABLED_style= \"max-width:90%; height:auto;\" >t; is the equation. (t (days) is on the x axis and the radius(km) is on the y axis):<BR>\n" );
document.write( "if you graphed it would look like this:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+graph%28+300%2C+200%2C+-20%2C+60%2C+-50%2C+200%2C+%28107%2F40%29x+%29+ ALIGN=MIDDLE  ALT=\"+graph%28+300%2C+200%2C+-20%2C+60%2C+-50%2C+200%2C+%28107%2F40%29x+%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "Using your calibrated eyeball, you can see on the graph that after 40 days the radius is about 100 km<BR>\n" );
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document.write( "Did this make sense? Did it help you? </SPAN>\n" );
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