If C₁ = {x : x ∈ ℕ and x is a factor of both 12 and 18}, what is C₁?
Answer and explanation
Correct answer: C₁ = {1, 2, 3, 6}
The positive factors of 12 are 1, 2, 3, 4, 6, and 12. The positive factors of 18 are 1, 2, 3, 6, 9, and 18. The elements common to both lists are therefore 1, 2, 3, and 6, so C₁ = {1, 2, 3, 6}. Because a fixed natural number has only finitely many factors, this is a finite set.
Frequently asked questions
What is the correct answer to this question?
C₁ = {1, 2, 3, 6}
Why is this the correct answer?
The positive factors of 12 are 1, 2, 3, 4, 6, and 12. The positive factors of 18 are 1, 2, 3, 6, 9, and 18. The elements common to both lists are therefore 1, 2, 3, and 6, so C₁ = {1, 2, 3, 6}. Because a fixed natural number has only finitely many factors, this is a finite set.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: The Empty Set, Finite and Infinite Sets, Equal Sets.