If n(U) = 240, n(A ∪ B) = 157, and n(Aᶜ ∩ Bᶜ) = 83, which relation is true?
Answer and explanation
Correct answer: n(A ∪ B) + n(Aᶜ ∩ Bᶜ) = n(U)
By De Morgan’s law, Aᶜ ∩ Bᶜ = (A ∪ B)ᶜ. Therefore, the sets A ∪ B and Aᶜ ∩ Bᶜ are complementary regions of the universal set U. Their cardinalities add to n(U): 157 + 83 = 240. Hence option A is the only true relation; the other options confuse intersection, union, or equality of unrelated regions.
Frequently asked questions
What is the correct answer to this question?
n(A ∪ B) + n(Aᶜ ∩ Bᶜ) = n(U)
Why is this the correct answer?
By De Morgan’s law, Aᶜ ∩ Bᶜ = (A ∪ B)ᶜ. Therefore, the sets A ∪ B and Aᶜ ∩ Bᶜ are complementary regions of the universal set U. Their cardinalities add to n(U): 157 + 83 = 240. Hence option A is the only true relation; the other options confuse intersection, union, or equality of unrelated regions.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Venn Diagrams.