Question

Let n(A) = 4 and n(B) = 6. Then the number of one - one functions from A to B is

• A. 120
• B. 360
• C. 24
• D. none of these

Answer 1

The correct option is B 360

$n\left(A\right)=4$

$n\left(B\right)=6$

$\text{Number of one-one functions}(A\to B)$

$=6c_4\times 4!$

$=\frac{6!}{2!4!}\times 4!$

$=6\times 5\times 4\times 3$

$=360$