document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1000955>Question 1000955</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The problem goes like this: \r<BR>\n" );
document.write( "\n" );
document.write( "There are 10 detergent brands that are to be ranked. Determine the probability that a.) brand A is ranked first and b.) that brand A is in the top 3 brands.\r<BR>\n" );
document.write( "\n" );
document.write( "I know that the answer to the first is .10, because each of the brands have 1/10 probability of ranking first. I'm not sure how to solve for b.)\r<BR>\n" );
document.write( "\n" );
document.write( "An explanation would be great with the solution.  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #618268 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=618268\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Probability that A is in the top three brands.<BR>\n" );
document.write( "It may occur first, second, or third.<BR>\n" );
document.write( "(1/10) for the first, or 0.10<BR>\n" );
document.write( "(9/10)*(1/9) for the second, which is 0.10. It can't be first, but all the others can be. <BR>\n" );
document.write( "(9/10)(8/9)(1/8) for the third, which is 72/720 or 0.10.  The first is 9/10, the second is 8/9, because there are nine left and 8 non-As to choose from<BR>\n" );
document.write( "The probability is 0.3.<BR>\n" );
document.write( "The assumption is that all brands have an equal chance of being chosen.<BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );