If n(B) = 15 and n(A ∩ B) = 6, what is n(B − A)?
Advertisement
Answer and explanation
Correct answer: 9
The difference B − A contains those elements that belong to B but do not belong to A. The intersection A ∩ B contains the 6 elements common to both sets. Since B has 15 elements in total, remove its 6 common elements: n(B − A) = n(B) − n(A ∩ B) = 15 − 6 = 9. Therefore, option A is correct.
Frequently asked questions
What is the correct answer to this question?
9
Why is this the correct answer?
The difference B − A contains those elements that belong to B but do not belong to A. The intersection A ∩ B contains the 6 elements common to both sets. Since B has 15 elements in total, remove its 6 common elements: n(B − A) = n(B) − n(A ∩ B) = 15 − 6 = 9. Therefore, option A is correct.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Operations on Sets (Union, Intersection, Difference).
Advertisement