Question

The set A has 4 elements and the set B has 5 elements then the number of injective mapping that can be defined from A to B
a. 144
b. 72
c. 60
d. 120​

Answer 1

Answer:

Let f be such a function. Now, f takes inputs from set A whereas the output value of f comes from set B.

Using the fact that injective functions are one-one and onto, f(1) can take 5 values, f(2) can then take only 4 values ,f(3) can take only 3 and f(4) only 2. Hence the total number of

functions are 5×4×3×2=120.