document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=984758>Question 984758</A>: <I><SPAN STYLE=\"word-break: break-all;\"> the speed of motorists on a highway is normally distrubuted with a mean of 120km/h and variance of 240. If the metro-police wants to stop the 5% fastest motorists, what is the cut-off speed so that all cars which travel at a speed faster than the cut-off speed will be stopped </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #605582 by </B><A HREF=/tutors/aboutme.mpl?userid=Boreal><B>Boreal(15235)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Boreal><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=Boreal><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=605582\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> I want the standard deviation, which is sqrt (variance)=sqrt(240)=15.49<BR>\n" );
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document.write( "The fastest 95% of the motorists will have a z-score greater than or equal to 1.645.<BR>\n" );
document.write( "z=(x-mean)/sd<BR>\n" );
document.write( "1.645=(speed-average/sd<BR>\n" );
document.write( "1.645=(x-120)/15.49<BR>\n" );
document.write( "multiply both sides by 15.49<BR>\n" );
document.write( "26.14=x-120<BR>\n" );
document.write( "x=146.14 km/h or faster than 147 km/h rounding upward. </SPAN>\n" );
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