If n(A) = 8, n(B) = 6, and n(A ∪ B) = 10, what is n(A ∩ B)?
Answer and explanation
Correct answer: 4
For two finite sets, the inclusion–exclusion formula is n(A ∪ B) = n(A) + n(B) − n(A ∩ B). Therefore, n(A ∩ B) = 8 + 6 − 10 = 4. Hence, four elements are common to A and B. Option 2 is merely the difference between the set sizes, 14 ignores the overlap, and 10 is the cardinality of the union.
Frequently asked questions
What is the correct answer to this question?
4
Why is this the correct answer?
For two finite sets, the inclusion–exclusion formula is n(A ∪ B) = n(A) + n(B) − n(A ∩ B). Therefore, n(A ∩ B) = 8 + 6 − 10 = 4. Hence, four elements are common to A and B. Option 2 is merely the difference between the set sizes, 14 ignores the overlap, and 10 is the cardinality of the union.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Operations on Sets (Union, Intersection, Difference).