Maths-
General
Easy

Question

In a town of 10000 familiesblankit was found that 40% families buy newspaper A comma 20 percent sign families buy newspaper B and 10% families buy newspaper C comma blank 5 percent sign families buy A and B comma 3% buy B and C and 4% buy A and C. If 2% families buy all the three newspapers, then the number of families which buy A only is

  1. 3100  
  2. 3300  
  3. 2900  
  4. 1400  

The correct answer is: 3300


    We have,
    N equals 10000 comma n open parentheses A close parentheses equals 40 percent sign blank o f blank 10000 equals 4000 comma
    n open parentheses B close parentheses equals 2000 comma n open parentheses C close parentheses equals 1000 comma n open parentheses A intersection B close parentheses equals 500 comma
    n open parentheses B intersection C close parentheses equals 300 comma n open parentheses C intersection A close parentheses equals 400 comma n open parentheses A intersection B intersection C close parentheses equals 200
    Now,
    Required number of families =
    n open parentheses A intersection stack B with minus on top intersection stack C with minus on top close parentheses equals n left parenthesis A intersection open parentheses B union C close parentheses to the power of ´ end exponent right parenthesis
    equals n open parentheses A close parentheses minus n left parenthesis A intersection left parenthesis B union C right parenthesis right parenthesis
    equals n open parentheses A close parentheses minus n open parentheses open parentheses A intersection B close parentheses union open parentheses A intersection C close parentheses close parentheses
    equals n open parentheses A close parentheses minus open curly brackets n open parentheses A intersection B close parentheses plus n open parentheses A intersection C close parentheses minus n open parentheses A intersection B intersection C close parentheses close curly brackets
    equals 4000 minus open parentheses 500 plus 400 minus 200 close parentheses equals 3300

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