Results 1 to 2 of 2

Math Help - subset

  1. #1
    Member
    Joined
    Dec 2008
    Posts
    86

    subset

    hello..i need help please

    Let
    S be a set with n elements.
    (a) How many subsets of
    S have 3 elements ?

    (b)How many subsets of
    S have more than 2 elements ?


    thank you
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Lord of certain Rings
    Isomorphism's Avatar
    Joined
    Dec 2007
    From
    IISc, Bangalore
    Posts
    1,465
    Thanks
    6
    Quote Originally Posted by qwerty321 View Post
    hello..i need help please

    Let
    S be a set with n elements.
    (a) How many subsets of
    S have 3 elements ?

    (b)How many subsets of
    S have more than 2 elements ?


    thank you
    (a)Its the same as asking, in how many ways can you pick three elements out of n?

    (b) The answer to how many subsets have greater than or equal to 2 elements is 2^n - 1 - n. Can you figure out why?
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. [SOLVED] Proof that if A is a subset of P(A), P(A) is a subset of P(P(A))
    Posted in the Discrete Math Forum
    Replies: 12
    Last Post: May 23rd 2011, 05:26 PM
  2. subset
    Posted in the Differential Geometry Forum
    Replies: 1
    Last Post: February 4th 2011, 02:14 PM
  3. Proof on Openness of a Subset and a Function of This Subset
    Posted in the Differential Geometry Forum
    Replies: 3
    Last Post: October 24th 2010, 10:04 PM
  4. subset U subset is NOT subspace of Superset?
    Posted in the Advanced Algebra Forum
    Replies: 1
    Last Post: September 20th 2009, 05:17 PM
  5. Subset tst
    Posted in the Advanced Algebra Forum
    Replies: 2
    Last Post: December 11th 2007, 10:28 AM

Search Tags


/mathhelpforum @mathhelpforum