document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=622155>Question 622155</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A sample of 4 telephones is selected from a shipment of 20 phones.  There are 5 defective telephones in the shipment. How many of the samples of 4 phones do not include any of the defective ones? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #391260 by </B><A HREF=/tutors/aboutme.mpl?userid=math-vortex><B>math-vortex(648)</B></A><img src=\"/images/stars/stars-11.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=math-vortex><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=math-vortex><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=391260\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Hi, there--<BR>\n" );
document.write( ".<BR>\n" );
document.write( "This is a combinations problem. We want to choose samples with four non-defective phones and zero defective phones. In the shipment of 20 phones, five are defective. That means that 15 phones are non-defective.<BR>\n" );
document.write( ".<BR>\n" );
document.write( "The total number of ways to choose four good non-defective phones is 15-choose-4, or 15C4.<BR>\n" );
document.write( ".<BR>\n" );
document.write( "15C4 = 15! / (4! 11!)<BR>\n" );
document.write( "15C4 = (15*14*13*12*11!) / (4*3*2*1*11!)<BR>\n" );
document.write( "15C4 =1365<BR>\n" );
document.write( ".<BR>\n" );
document.write( "There 1,365 ways to choose four working phones from the shipment.<BR>\n" );
document.write( ".<BR>\n" );
document.write( "Hope this helps!<BR>\n" );
document.write( ".<BR>\n" );
document.write( "Ms.Figgy<BR>\n" );
document.write( "math.in.the.vortex@gmail.com </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );