Given,

A= {1, 2}, B= {3, 4}

n(A) = 2 (Number of elements in set A).

n(B) = 2 (Number of elements in set B).

We know,

n(A × B) = n(A) × n(B) = 2 × 2 = 4

∴ Number of relations from A to B are 4.

NOTE:

Given,

A= {1, 2}, B= {3, 4}

A relation from A to B can be defined as:

A × B = {(1, 3), (1, 4), (2, 3), (2, 4)}

∴ Number of relations from A to B are 4