Answer: mn
Explanation:
A set refers to a well-defined collection of items.
For example : Set of natural numbers (N)
Set of rational numbers (Q).
A Cartesian product is a product of two different sets .
such as M= {1,2} and N={3,4}
Then M x N ={(1,3) , (1,4) , (2,3) , (2,4)}
According to the properties of the Cartesian product of sets, if a set P has 'k' elements and an another set Q has 'r' elements , then the number of different elements in P x Q =kr
Similarly , if A has m elements and B has n elements , then A x B has 'mn' elements.
∴ The number of ifferent elements does A × B have if A has m elements and B has n elements= mn