Please help!!

Discussion in 'Personal Homework Help' started by Becky Hamilton, Mar 19, 2018.

  1. Becky Hamilton

    Becky Hamilton New Member

    Find the value of |A| if:
    (1) |P(A)| = 4
    (2) |B| = |A|+ 1 and |A×B| = 30
    (3) |B| = |A|+ 2 and |P(B)|−|P(A)| = 24
     

  2. math_celebrity

    math_celebrity Administrator Staff Member

    (1), how can probability be greater than 1?
     

  3. Becky Hamilton

    Becky Hamilton New Member

    It is a set theory question
     

  4. math_celebrity

    math_celebrity Administrator Staff Member

    (1) |P(A)| = 4 <-- Cardinality of the power set is 4, which means we have 2^n = 4. |A| = 2

    (2) |B| = |A|+ 1 and |A×B| = 30
    |B| = 6 if |A| = 5 and |A x B| = 30

    (3) |B| = |A|+ 2 and |P(B)|−|P(A)| = 24
    Since |B| = |A|+ 2, we have: 2^(a + 2) - 2^a = 24
    2^a(2^2 - 1) = 24
    2^a(3) = 24
    2^a = 8
    |A |= 3

    To check, we have |B| = |A| + 2 --> 3 + 2 = 5

    So |P(B)| = 2^5 = 32

    |P(A)| = 2^3 = 8
    And 32 - 8 = 24
     
    Becky Hamilton likes this.

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