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

  • question_answer
    Which of the following is/are true?
    I. If A is a subset of the universal set U then its complement A? is also a subset of U.
    II. If \[U=\{1,2,3,....,10\}\] and \[A=\{1,3,5,7,9\}\]then \[{{(A')}^{'}}=A.\]

    A) Only I is true

    B) Only II is true

    C) Both I and II are true

    D) None of these

    Correct Answer: C

    Solution :

    [c]If A is a subset of the universal set U, then its complement A? is also a subset of U. We have, \[A'=\{2,\,\,4,\,\,6,\,\,8,\,\,10\}\] Hence, \[(A')'=\{x:x\in U\,\,and\,\,x\notin A'\}=\{1,3,5,7,9\}=A\] It is clear from the definition of the complement that for any subset of the universal set U, we have \[(A')'=A\]


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