document.write( "Question 1172403: In a survey of 600 people in Windhoek, the results of the survey showed that
\n" ); document.write( "250 people read The Namibian, 260 people read The Mmegi, and 260 people
\n" ); document.write( "read The Daily Mirror. Additionally, 90 people read both The Namibian and The
\n" ); document.write( "Daily Mirror, and 110 read both The Namibian and Mmegi, 80 read both The
\n" ); document.write( "Mmegi and The Daily Mirror and 80 did not read any of the above newspapers.
\n" ); document.write( "Find the number of people who read all the three newspapers. \n" ); document.write( "
Algebra.Com's Answer #797416 by ikleyn(52847)\"\" \"About 
You can put this solution on YOUR website!
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\n" ); document.write( "In a survey of 600 people in Windhoek, the results of the survey showed that
\n" ); document.write( "250 people read The Namibian, 260 people read The Mmegi, and 260 people
\n" ); document.write( "read The Daily Mirror. Additionally, 90 people read both The Namibian and The
\n" ); document.write( "Daily Mirror, and 110 read both The Namibian and Mmegi, 80 read both The
\n" ); document.write( "Mmegi and The Daily Mirror and 80 did not read any of the above newspapers.
\n" ); document.write( "Find the number of people who read all the three newspapers.
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document.write( "If A, B, and C are three subset in an finite universal set U, then\r\n" );
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document.write( "    n(A U B U C) = n(A) + n(B) + n(C) - n(A ∩ B) - n(A ∩ C) - n(B ∩ C) + n(A ∩ B ∩ C),\r\n" );
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document.write( "where n(X)  denotes the number of elements in subset X.\r\n" );
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document.write( "Apply this formula for the given situation. Substitute the given numbers into the formula.\r\n" );
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document.write( "You will get\r\n" );
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document.write( "    600 - 80 = 250 + 260 + 260 - 90 - 110 - 80 + n(A ∩ B ∩ C),\r\n" );
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document.write( "or\r\n" );
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document.write( "       520   =          490                    + n(A ∩ B ∩ C),\r\n" );
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document.write( "which implies\r\n" );
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document.write( "       n(A ∩ B ∩ C) = 520 - 490 = 30.\r\n" );
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document.write( "ANSWER.  30 persons read all three newpapers.\r\n" );
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\n" ); document.write( "\n" ); document.write( "To see many other similar solved problems of this kind, look into the lessons\r
\n" ); document.write( "\n" ); document.write( "    - Counting elements in sub-sets of a given finite set\r
\n" ); document.write( "\n" ); document.write( "    - Advanced problems on counting elements in sub-sets of a given finite set\r
\n" ); document.write( "\n" ); document.write( "    - Challenging problems on counting elements in subsets of a given finite set \r
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