document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1145993>Question 1145993</A>: <I><SPAN STYLE=\"word-break: break-all;\">  A computer retail store has 9 personal computers in stock. A buyer wants to purchase 4 of them. Unknown to either the retail store or the buyer, 4 of the computers in stock have defective hard drives. Assume that the computers are selected at random.\r<BR>\n" );
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document.write( "(a)  In how many different ways can the 4 computers be chosen?\r<BR>\n" );
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document.write( "(b)  What is the probability that exactly one of the computers will be defective?\r<BR>\n" );
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document.write( "(c)  What is the probability that at least one of the computers selected is defective?<BR>\n" );
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document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #767369 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=767369\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> <i>(a) In how many different ways can the 4 computers be chosen?</i><BR>\n" );
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document.write( "9C4 = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=9%21%2F%284%21%2A5%21%29 ALIGN=MIDDLE  ALT=\"9%21%2F%284%21%2A5%21%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > = 126<BR>\n" );
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document.write( "Since 4 out of the 9 computers are defective, this means there is a 0.4444 probability a randomly chosen computer is defective.  (You will need to know this to answer the next two questions.)<BR>\n" );
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document.write( "<i>(b) What is the probability that exactly one of the computers will be defective?</i><BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%280.4444%29%5E1+%2A+%280.5556%29%5E3+%2A+%284%21%2F%281%21%2A3%21%29%29 ALIGN=MIDDLE  ALT=\"%280.4444%29%5E1+%2A+%280.5556%29%5E3+%2A+%284%21%2F%281%21%2A3%21%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > = 0.4444 * 0.1715 * 4 = 0.3049<BR>\n" );
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document.write( "<i>(c)  What is the probability that at least one of the computers selected is defective?</i><BR>\n" );
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document.write( "To do this, you compute the probability that NONE of the four computers is defective, then subtract this result from 1:<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=1+-+%280.5556%29%5E4 ALIGN=MIDDLE  ALT=\"1+-+%280.5556%29%5E4\"   DISABLED_style= \"max-width:90%; height:auto;\" > = 1 - 0.0953 = 0.9047 </SPAN>\n" );
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