document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=929035>Question 929035</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The stopping distance d of a car after the brakes are applied varies directly as the square of the speed r. If a car traveling 20 mph can stop in 20 ft, how many feet will it take the same car to sop when it is traveling 100 mph? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #806961 by </B><A HREF=/tutors/aboutme.mpl?userid=greenestamps><B>greenestamps(13203)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=greenestamps><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=greenestamps><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=806961\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> <br><BR>\n" );
document.write( "for tutor @CubeyThePenguin....<br><BR>\n" );
document.write( "(1) Your cryptic calculations with no explanation are of no use to the student who is trying to learn how to solve the problem.<br><BR>\n" );
document.write( "(2) I can't tell what the calculations you show are supposed to be doing to solve the problem.  Remember, your purpose as a tutor here is not to show that you know how to solve a problem; your purpose is to help the student learn how to solve the problem.<br><BR>\n" );
document.write( "(3) And in this case, whatever your calculations were supposed to be doing, they gave the wrong answer....<br><BR>\n" );
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document.write( "Informally, the solution is simple.  Since the stopping distance varies directly as the square of the speed, a speed 5 times as great means a stopping distance 5^2=25 times as great.  ANSWER: 25(20 feet) = 500 feet.<br><BR>\n" );
document.write( "More formally....<br><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d+=+kr%5E2 ALIGN=MIDDLE  ALT=\"d+=+kr%5E2\"   DISABLED_style= \"max-width:90%; height:auto;\" ><br><BR>\n" );
document.write( "Find the constant of proportionality knowing that the stopping distance is 20 feet at 20mph.<br><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=20+=+k%2820%5E2%29 ALIGN=MIDDLE  ALT=\"20+=+k%2820%5E2%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=20+=+400k ALIGN=MIDDLE  ALT=\"20+=+400k\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=k+=+1%2F20 ALIGN=MIDDLE  ALT=\"k+=+1%2F20\"   DISABLED_style= \"max-width:90%; height:auto;\" ><br><BR>\n" );
document.write( "Use that constant to find the sopping distance if the speed is 100mph.<br><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d+=+kr%5E2 ALIGN=MIDDLE  ALT=\"d+=+kr%5E2\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d+=+%281%2F20%29%28100%5E2%29+=+10000%2F20+=+500 ALIGN=MIDDLE  ALT=\"d+=+%281%2F20%29%28100%5E2%29+=+10000%2F20+=+500\"   DISABLED_style= \"max-width:90%; height:auto;\" ><br><BR>\n" );
document.write( "ANSWER: 500 feet<br><BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );