document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1179137>Question 1179137</A>: <I><SPAN STYLE=\"word-break: break-all;\"> B. In a Statistics class, there are 28 juniors and 12 seniors; 18 of the<BR>\n" );
document.write( "juniors are males and 5 of the seniors are females. If a student is<BR>\n" );
document.write( "selected at random, find the probability of selecting the following:\r<BR>\n" );
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document.write( "1. A junior<BR>\n" );
document.write( "2. A male<BR>\n" );
document.write( "3. A junior or a female​ </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #808627 by </B><A HREF=/tutors/aboutme.mpl?userid=Theo><B>Theo(13342)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Theo><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=Theo><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=808627\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> make a table as shown below.\\r<BR>\n" );
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document.write( "                    junior           senior          total\r\n" );
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document.write( "male                  18               7               25\r\n" );
document.write( "female                10               5               15\r\n" );
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document.write( "total                 28              12               40\r\n" );
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document.write( "</PRE>\r<BR>\n" );
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document.write( "there are 28 juniors out of a total of 40 so the probability of a student, selected at random, of being a junior is 28/40.\r<BR>\n" );
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document.write( "there are 25 males out of a total of 40 so the probability of a student, selected at random, of being a male is 25/40.\r<BR>\n" );
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document.write( "there are 28 juniors out of a total of 40, so the probability of a student, selected at random, of being a junior is 28/40.<BR>\n" );
document.write( "there are 15 females out of a total of 40, so the probability of a student, selected at random, of being a female is 15/40.\r<BR>\n" );
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document.write( "the total is 28 + 15 = 43 out of 40, but .....<BR>\n" );
document.write( "10 of those are both a female and a junior.<BR>\n" );
document.write( "as such, they are being double counted, 10 as a junior and 10 as a female.<BR>\n" );
document.write( "to avoid the double counting, you have to subtract 10 from the total to get a total of 28 + 15 - 10 = 33 that are either a junior or a female.\r<BR>\n" );
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document.write( "the formulas take care of this.\r<BR>\n" );
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document.write( "let a = the probability of being a junior.<BR>\n" );
document.write( "let b = the probability of being a female.\r<BR>\n" );
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document.write( "the formula states that p(a or b) = p(a) + p(b) - p(a and b)\r<BR>\n" );
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document.write( "that becomes 28/40 + 15/40 - 10/40 = (28 + 15 - 10) / 40 = 33/40.\r<BR>\n" );
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document.write( " </SPAN>\n" );
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