document.write( "Question 1134540: 400 students are surveyed about the pets they have. 250 have a dog, 190 have a cat
\n" ); document.write( "and 160 have a dog and a cat. What is the probability that a student has a dog?\r
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Algebra.Com's Answer #751957 by ikleyn(52780) $\"\"$ $\"About$

You can put this solution on YOUR website!
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document.write( "There is a universal set U of 400 students.\r\n" );
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document.write( "There is a subset D of 250 students that have a dog.\r\n" );
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document.write( "There is a subset C of 190 students that have a cat.\r\n" );
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document.write( "And there is the intersection (D n C) of these subsets, which contains 160 students that have a dog AND a cat.\r\n" );
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document.write( "Then the number of students who have a dog OR a cat is  n(D U C) = n(D) + n(C) - n(D n C) = 250 + 190 - 160 = 280.\r\n" );
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document.write( "The answer to the first question is  P(D) =  =  = .\r\n" );
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document.write( "The answer to the second question is  P(D U C) =  =  = .\r\n" );
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\n" ); document.write( "\n" ); document.write( "If you want to learn more about the formula to calculate the union of subsets, look into my lesson\r
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