document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=254875>Question 254875</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Nine customers at a supermarket are asked if they use brand X laundry soap. In general, 22% of the population use this brand.  What is the probability that among the nine, more than two people use brand X? (round answer to 4 decimal places).\r<BR>\n" );
document.write( "\n" );
document.write( "I keep getting impossible answers so I'm not sure if I'm setting the problem up wrong, or calculating it wrong. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #187187 by </B><A HREF=/tutors/aboutme.mpl?userid=scott8148><B>scott8148(6628)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=scott8148><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=scott8148><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=187187\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> this is a binomial expansion problem<BR>\n" );
document.write( "people either use (U with probability .22) or don't use (D with probability .78)\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "you need the sum of the first seven terms of the expansion (U + D)^9\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "it is easier to sum the last three terms and subtract from 1\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "1 - [36(U^2 D^7) + 9(U D^8) + (D^9)]\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "1 - [36(.22^2 * .78^7) + 9(.22 * .78^8) + (.78^9)] </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );