How many elements does 𝒫(𝒫(∅)) have?
Answer and explanation
Correct answer: 2
First evaluate the inner power set. Since ∅ has no elements, 𝒫(∅) = {∅}, which has one element. Now take the power set of this one-element set. A one-element set has 2¹ = 2 subsets: ∅ and {∅}. Therefore, 𝒫(𝒫(∅)) contains two elements. The two power-set operations must be applied successively from the inside outward.
Frequently asked questions
What is the correct answer to this question?
2
Why is this the correct answer?
First evaluate the inner power set. Since ∅ has no elements, 𝒫(∅) = {∅}, which has one element. Now take the power set of this one-element set. A one-element set has 2¹ = 2 subsets: ∅ and {∅}. Therefore, 𝒫(𝒫(∅)) contains two elements. The two power-set operations must be applied successively from the inside outward.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Power Set and Subsets.