document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1137335>Question 1137335</A>: <I><SPAN STYLE=\"word-break: break-all;\"> If the probability that a fluorescent light has a useful life of at least 800 hours is 0.9, find the probabilities that among 20 such lights<BR>\n" );
document.write( "(a) exactly 18 will have a useful life of at least 800 hours;<BR>\n" );
document.write( "(b) at least 15 will have a useful life of at least 800 hours<BR>\n" );
document.write( " <BR>\n" );
document.write( "ANS: (a) 0.2852 ; (b)0.9887 </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #755215 by </B><A HREF=/tutors/aboutme.mpl?userid=VFBundy><B>VFBundy(438)</B></A><img src=\"/images/stars/stars-10.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=VFBundy><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=VFBundy><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=755215\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> <b>(a) exactly 18 will have a useful life of at least 800 hours</b><BR>\n" );
document.write( "<pr><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%280.9%29%5E18+%2A+%280.1%29%5E2+%2A+%2820%21%2F%2818%21%2A2%21%29%29 ALIGN=MIDDLE  ALT=\"%280.9%29%5E18+%2A+%280.1%29%5E2+%2A+%2820%21%2F%2818%21%2A2%21%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > = 0.2852<BR>\n" );
document.write( "<pr><BR>\n" );
document.write( "<b>(b) at least 15 will have a useful life of at least 800 hours</b><BR>\n" );
document.write( "<pr><BR>\n" );
document.write( "P(exactly 15 with useful life of at least 800 hours) = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%280.9%29%5E15+%2A+%280.1%29%5E5+%2A+%2820%21%2F%2815%21%2A5%21%29%29 ALIGN=MIDDLE  ALT=\"%280.9%29%5E15+%2A+%280.1%29%5E5+%2A+%2820%21%2F%2815%21%2A5%21%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > = 0.0319<BR>\n" );
document.write( "P(exactly 16 with useful life of at least 800 hours) = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%280.9%29%5E16+%2A+%280.1%29%5E4+%2A+%2820%21%2F%2816%21%2A4%21%29%29 ALIGN=MIDDLE  ALT=\"%280.9%29%5E16+%2A+%280.1%29%5E4+%2A+%2820%21%2F%2816%21%2A4%21%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > = 0.0898<BR>\n" );
document.write( "P(exactly 17 with useful life of at least 800 hours) = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%280.9%29%5E17+%2A+%280.1%29%5E3+%2A+%2820%21%2F%2817%21%2A3%21%29%29 ALIGN=MIDDLE  ALT=\"%280.9%29%5E17+%2A+%280.1%29%5E3+%2A+%2820%21%2F%2817%21%2A3%21%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > = 0.1901<BR>\n" );
document.write( "P(exactly 18 with useful life of at least 800 hours) = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%280.9%29%5E18+%2A+%280.1%29%5E2+%2A+%2820%21%2F%2818%21%2A2%21%29%29 ALIGN=MIDDLE  ALT=\"%280.9%29%5E18+%2A+%280.1%29%5E2+%2A+%2820%21%2F%2818%21%2A2%21%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > = 0.2852<BR>\n" );
document.write( "P(exactly 19 with useful life of at least 800 hours) = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%280.9%29%5E19+%2A+%280.1%29%5E1+%2A+%2820%21%2F%2819%21%2A1%21%29%29 ALIGN=MIDDLE  ALT=\"%280.9%29%5E19+%2A+%280.1%29%5E1+%2A+%2820%21%2F%2819%21%2A1%21%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > = 0.2702<BR>\n" );
document.write( "P(exactly 20 with useful life of at least 800 hours) = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%280.9%29%5E20 ALIGN=MIDDLE  ALT=\"%280.9%29%5E20\"   DISABLED_style= \"max-width:90%; height:auto;\" > = 0.1216<BR>\n" );
document.write( "<pr><BR>\n" );
document.write( "P(at least 15 will have a useful life of at least 800 hours) = 0.0319 + 0.0898 + 0.1901 + 0.2852 + 0.2702 + 0.1216 = 0.9888 </SPAN>\n" );
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