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Homework Help: Quick relations question.

  1. Oct 20, 2013 #1
    1. The problem statement, all variables and given/known data

    True or False: Given that A = {a,b,c} and B={0,1,2,3,4}, there are 32768 binary relations from A to B

    I assume there is some simple way to tell how many relations there are given two different sets, but I don't know it. Factorials? Powers? I'm not sure what.
  2. jcsd
  3. Oct 20, 2013 #2


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    A "binary relation from A to B" is formally a subset of [itex]A \times B[/itex], so the number of such relations is the number of subsets of [itex]A \times B[/itex].
  4. Oct 20, 2013 #3


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    Try and work it out. How many total ordered pairs are there in AxB? Now each ordered pair can either be in the relation or not.
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