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JEE Main & Advanced Mathematics Sets Question Bank Self Evaluation Test - Sets

  • question_answer
    If n  = 115, n  = 326, n(A - B) = 47, then what in \[n(A\cup B)\] equal to?

    A) 373

    B) 165

    C) 370                              

    D) 394

    Correct Answer: A

    Solution :

    [a]We know, for two sets A and B \[A-B=A-(A\cap B)\] \[\therefore n(A-B)=n(A)-n(A\cap B)\] Given, \[n(A)=115,n(B)=326\] and \[n(A-B)=47.\] \[\Rightarrow 47=115-n(A\cap B)\] \[\Rightarrow n(A\cap B)=68\] Consider \[n(A\cup B)=n(A)+n(B)-n(A\cap B)\] \[=115+326-68=373\]                           


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