If A ⊆ B ⊆ U, which relation is always true?
Answer and explanation
Correct answer: Bᶜ ⊆ Aᶜ
Taking complements reverses the direction of set inclusion. Since every element of A is in B, any element that is not in B is certainly not in A. Therefore every element of Bᶜ belongs to Aᶜ, giving Bᶜ ⊆ Aᶜ. Equality is not guaranteed unless A and B are equal, so option B is the only always-true statement.
Frequently asked questions
What is the correct answer to this question?
Bᶜ ⊆ Aᶜ
Why is this the correct answer?
Taking complements reverses the direction of set inclusion. Since every element of A is in B, any element that is not in B is certainly not in A. Therefore every element of Bᶜ belongs to Aᶜ, giving Bᶜ ⊆ Aᶜ. Equality is not guaranteed unless A and B are equal, so option B is the only always-true statement.
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.