document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1182184>Question 1182184</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The length of time in hours before a mobile requires charging has a normal distribution with a mean of<BR>\n" );
document.write( "100 hours and a standard deviation of 15 hours.<BR>\n" );
document.write( "a) Find the probability that the time before charging is greater than 127 hours.<BR>\n" );
document.write( "b) Find the 10th percentile<BR>\n" );
document.write( "c) You are about to go on a 6 hour trip. Given you last charged your phone 127 hours ago, what is<BR>\n" );
document.write( "the probability your mobile will not need charging until you complete the trip? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #812531 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=812531\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> z=(x-mean)/sd<BR>\n" );
document.write( "z>27/15=1.8 and that probability is 0.0359<BR>\n" );
document.write( "-<BR>\n" );
document.write( "10th percentile for z is -1.282<BR>\n" );
document.write( "-1.282=(x-mean)/15<BR>\n" );
document.write( "-19.22=x-mean (didn't round z until here)<BR>\n" );
document.write( "x=80.78 hours<BR>\n" );
document.write( "-<BR>\n" );
document.write( "Essentially want the probability of the mobile phone's going 133 hours without charging, and that is z>33/15 or z>2.2<BR>\n" );
document.write( "this probability is 0.0139<BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );