Let $A$ and $B$ be sets with cardinalities $m$ and $n$ respectively. The number of one-one mappings from $A$ to $B$, when $m < n$, is
Answer: B Ref: Page 33 of http://www.cs.toronto.edu/~stacho/macm101-2.pdf
Ref:
Answer is ^{n}P_{m}
Gatecse
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