document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1160252>Question 1160252</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A lab network consisting of 20 computers was attacked by a computer virus. This virus enters each computer with probability 0.4, independently of other computers. Find the probability that it entered at least one computer. Ans: 0.99996 </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #783527 by </B><A HREF=/tutors/aboutme.mpl?userid=Theo><B>Theo(13342)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Theo><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=Theo><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=783527\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> p = .4<BR>\n" );
document.write( "q = 1 - p = .6<BR>\n" );
document.write( "n = 20<BR>\n" );
document.write( "p(x) = p^x * q^(n-x) * c(n,x)<BR>\n" );
document.write( "this is the binomial probability formula you would use to solve this problem.<BR>\n" );
document.write( "the probability that it entered at least 1 computer is equal to 1 minus the probability that it entered 0 computers.<BR>\n" );
document.write( "p(0) = .4^0 * .6^20 * c(20,0) = 3.65615844 * 10^-5.<BR>\n" );
document.write( "1 minus that = .9999634384.<BR>\n" );
document.write( "that's your answer.<BR>\n" );
document.write( "you can use your calculator to confirm.<BR>\n" );
document.write( "all the probabilities, given n = 10, p = .4 and q = .6 are shown below.<BR>\n" );
document.write( "the sum of all probabilities is equal to 1, as it should be.<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" src = \"http://theo.x10hosting.com/2020/053101.jpg\" alt=\"$$$\" ><BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );