Question

If set A and B are such that n(A) =8 and n (B)=12. if n(A U B) =9,find n(A n B)?​

Answer 1

Explanation:

9=8+12-X

9=20-X

-11= -X

X=11

Solve it by venn diagram rather memorizing formulae

Answer 2

`n(A\cap B)=n(A)+n(B)-n(A\cup B)`

Therefore

`n(A\cap B)=8+12-9=11`