No. of subsets of a set A having n elements =2n
No .of relations of a setA having 'm' elements to a set B with 'n' elements=2mn
No. of functions or mappings from a set having 'm' elements to a set B with 'n' elements=nm
No. of commutative binary operations on a set A having n elements=nn(n+1)/2
No. of onto functions from a set A with n elements to a set B with two elements=2n-2
No. of equivalence relations of a set A with n elements=2n-n
Moderation Team
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