Question

Let A = {1, 2, 3, 4, 5}; B = {2, 3, 6, 7}. Then the number of elements in $(A\times B)\cap (B\times A)$ is

• A. 18
• B. 6
• C. 4
• D. 0

Answer 1

Answer: (C)

Here A and B sets having 2 elements in common, so $A\times B$ and $B\times A$ have $2^2$ i.e., 4 elements in common. Hence, $n\left[\left(A\times B\right)\cap \left(B\times A\right)\right]=4$