Algebra.Com's Answer #415587 by Edwin McCravy(20060)![\"\"](\"/images/stars/stars-13.gif\")  
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say there are 5 male undergraduates, 2 female undergrduates, 2 male graduates, and 2 female graduates. find the probability of selecting an undergraduate or a female? i thought it was (7+4)/11 but thats just one ...
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document.write( "Your error is because when you add the 7 undergraduates and the 4\r\n" );
document.write( "females you are counting the 2 undergraduate females TWICE! You are\r\n" );
document.write( "counting them once among the 7 undergraduates and again among the\r\n" );
document.write( "4 females. Therefore you have to subtract those 2 once from the 7+4\r\n" );
document.write( "to keep from counting them twice. Therefore you get  =  .\r\n" );
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document.write( "You can also make a chart:\r\n" );
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document.write( " | grad | undergraduate || totals |\r\n" );
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document.write( "male | 2 | 5 || 7 |\r\n" );
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document.write( "female | 2 | 2 || 4 |\r\n" );
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document.write( "totals | 4 | 7 || 11 |\r\n" );
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document.write( "You only want to count the red numbers which add up to 9,\r\n" );
document.write( "So the probability is \r\n" );
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document.write( "Or you can use the formula that the other tutor used:\r\n" );
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document.write( "P(U or F) = P(U) + P(F) - P(U and F)\r\n" );
document.write( " =  +  -  \r\n" );
document.write( " = \r\n" );
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document.write( "Edwin
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