document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=149861>Question 149861</A>: <I><SPAN STYLE=\"word-break: break-all;\"> 18 out of 20 customers make a purchase. If three customers are selected randomly one at a time, what is the probability that all will make a purchase?\r<BR>\n" );
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document.write( "Please help. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #110044 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=110044\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> there are 20C3 (1140) possible groups of 3 in 20 __ some of these groups contain non-purchasers\r<BR>\n" );
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document.write( "there are 18C3 (816) possible groups of 3 in 18 __ none of these groups contain non-purchasers\r<BR>\n" );
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document.write( "probability of all purchasers is 816/1140 or 0.716 (approx)\r<BR>\n" );
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document.write( "if order of selection is thought to be important (permutation vs combination); the result will be the same </SPAN>\n" );
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