If |A| =kand |B| =m, how many relations are there between A and B? If in addition, |C| =n, how many ternary relations are there in AXBXC?

[Hint: recall the definition of a relation, and use of cardinality.]

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- Oct 16th 2008, 11:26 PMccliadiscrete mate
If |A| =

*k*and |B| =*m*, how many relations are there between A and B? If in addition, |C| =*n*, how many ternary relations are there in A*X*B*X*C?

[Hint: recall the definition of a relation, and use of cardinality.]

- Oct 17th 2008, 02:59 AMPlato
In general there are $\displaystyle 2^{\left| X \right|\left| Y \right|}$ relations between X & Y.

(Be careful. That number includes the empty relation some texts/instructors object.)