Question

If set A = {1, 2, 3} and set B = {2, 3, 5, 7} then the number of elements in A $\times$ B is .

• A. 10
• B. 11
• C. 12
• D. 13

Answer 1

The correct option is C 12

The number of elements in the cartesian product of two set is equal to the multiple of the number of the elements in both the sets.
Hence, the number of element in A $\times$ B = number of element in A $\times$ number of element in B = 3 $\times$ 4 = 12

A × B = {(1, 2), (1, 3), (1, 5), (1, 7), (2, 2), (2, 3), (2, 5), (2, 7), (3, 2), (3, 3), (3, 5), (3, 7)}