Question

if A={a,b,c,d},B={1,2,3,4,5}then number of one - one function from A to B is .....

Answer 1

A function is called a one-one function when there is one value of y corresponding to y.
Hence, for a there would be 5 options.
for b there would be 4 options and so on.
Therefore, the total number of one one functions is 5*4*3*2*1=120.
Hope it is correct

Answer 2

First take A elements as m and B elements as n

1. Now as per the given sum n>m so we should do n!/(n-m)!
2. So now m=4 and n=5
3. 5!/(5-4)!
4. That's 5!
5. And the answer is 120
6. As we know 5! is 120.