document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=579359>Question 579359</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A batch of 20 used automobile alternators contains 4 defectives. If 3 alternators are selected at random, find the probability of the events (Using the Rule of combinations):\r<BR>\n" );
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document.write( "A= None of the defective appears\r<BR>\n" );
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document.write( "B= Exactly two defective appears\r<BR>\n" );
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document.write( "The answer for A is .491 the answer for B is .084 but I can not figure out for the life of me how they got these answers.<BR>\n" );
document.write( "I've tried 3 of 20 which gave the 1140 total selections possible. Than if there is 4 defective and I want the probability of selecting none. I tried 0 of 4 which doesn't work 1 of 4 likewise doesn't work. I'm stuck. Please help I know this is probably going to be something so simple I am missing. <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 #370956 by </B><A HREF=/tutors/aboutme.mpl?userid=stanbon><B>stanbon(75887)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=stanbon><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/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=370956\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> A batch of 20 used automobile alternators contains 4 defectives and 16 good ones.<BR>\n" );
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document.write( "If 3 alternators are selected at random, find the probability of the events (Using the Rule of combinations): <BR>\n" );
document.write( "A= None of the defective appears<BR>\n" );
document.write( "P(no defectives) = P(3 good ones) = 16C3/20C3 = 0.4912<BR>\n" );
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document.write( "B= Exactly two defective appears<BR>\n" );
document.write( "P(x = 2) = 3C2(4/20)^2(16/20) = 3*(1/25)(4/5) = 12/125 = 0.0960<BR>\n" );
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document.write( "Note: The answer to \"B\" is not 0.084<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
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