A and B are two sets such that $n(A) = 5$ and $n(B) = 7$. The number of one-one functions from A to B is

2520

The correct answer is Option (3) → 2520

Given $n(A)=5$ and $n(B)=7$.

The number of one-one (injective) functions from $A$ to $B$ is

$7P5=\frac{7!}{(7-5)!}=\frac{7!}{2!}=7\times6\times5\times4\times3=2520$.

Number of one-one functions = 2520