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Math Help - inclusion exclusion principle help!

  1. #1
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    inclusion exclusion principle help!

    if A,B and C are finite sets with the following properties:
    B has 2 more elements than A;C is twice as big as B;
    AnB is the same size as AnC;B and C have no elements in common.
    prove that |AnBnC| is divisible by 2 (i.e. has an even number of elements)
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  2. #2
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    Re: inclusion exclusion principle help!

    Quote Originally Posted by university View Post
    if A,B and C are finite sets with the following properties:
    B has 2 more elements than A;C is twice as big as B;
    AnB is the same size as AnC;B and C have no elements in common.
    prove that |AnBnC| is divisible by 2 (i.e. has an even number of elements)
    Because "B and C have no elements in common", |A\cap B \cap C|=0.
    Zero is an even number.
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