If A ∪ B = B ∪ C and A ∩ B = B ∩ C, which conclusion must be true?
Answer and explanation
Correct answer: A = C
Consider any element x. If x is not in B, the union equality gives x ∈ A exactly when x ∈ C. If x is in B, the intersection equality gives x ∈ A exactly when x ∈ C. Thus every element belongs to A precisely when it belongs to C, so A = C. The other options do not necessarily follow.
Frequently asked questions
What is the correct answer to this question?
A = C
Why is this the correct answer?
Consider any element x. If x is not in B, the union equality gives x ∈ A exactly when x ∈ C. If x is in B, the intersection equality gives x ∈ A exactly when x ∈ C. Thus every element belongs to A precisely when it belongs to C, so A = C. The other options do not necessarily follow.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Operations on Sets (Union, Intersection, Difference).