If n(U) = 25, what is n(A ∪ Aᶜ)?
Answer and explanation
Correct answer: 25
Every element of the universal set U is either an element of A or an element of its complement Aᶜ. Consequently, A ∪ Aᶜ = U. Taking cardinalities on both sides gives n(A ∪ Aᶜ) = n(U) = 25. Therefore option A is correct. The result does not depend on the particular elements or size of A.
Frequently asked questions
What is the correct answer to this question?
25
Why is this the correct answer?
Every element of the universal set U is either an element of A or an element of its complement Aᶜ. Consequently, A ∪ Aᶜ = U. Taking cardinalities on both sides gives n(A ∪ Aᶜ) = n(U) = 25. Therefore option A is correct. The result does not depend on the particular elements or size of A.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Complement of a Set and Its Properties.