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Math Help - Cardinality of a set

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    Cardinality of a set

    What is the cardinality of the power set {NULL, a, {NULL}, {{NULL}}}? Why? I believe it is 3.
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    Re: Cardinality of a set

    Quote Originally Posted by peyton1983 View Post
    What is the cardinality of the power set {NULL, a, {NULL}, {{NULL}}}? Why? I believe it is 3.
    To be very clear, the given set is \left\{ {\emptyset ,\;a,\;\{ \emptyset \} ,\;\{ \{ \emptyset \} \} } \right\}.

    If that is correct, then that set contains four elements. So what is the carnality of its power set?
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    Re: Cardinality of a set

    Quote Originally Posted by Plato View Post
    To be very clear, the given set is \left\{ {\emptyset ,\;a,\;\{ \emptyset \} ,\;\{ \{ \emptyset \} \} } \right\}.

    If that is correct, then that set contains four elements.
    Unless a\in\left\{ {\emptyset ,\;\{ \emptyset \} ,\;\{ \{ \emptyset \} \} } \right\}, in which case it contains three elements.
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