Question

Given two sets $A=\{a,b,c,d\},B=\{b,c,d,e\}$, then $n\left[\right(A\times B)\cap (B\times A\left)\right]$ is

• A. $3$
• B. $16$
• C. $9$
• D. $4$

Answer 1

The correct option is C $9$

$n\left[\right(A\times B)\cap (B\times A\left)\right]=n(A\cap B)\times n(B\cap A)=3\times 3=9$