If \(A=\{1,2,3\}\) and \(B=\{3,2,1\}\), what is \(A\cup B\)?
Answer and explanation
Correct answer: \(\{1,2,3\}\)
In a set, the order in which elements are written does not matter, and repeated elements are counted only once. Thus \(A\) and \(B\) contain exactly the same elements: 1, 2, and 3. Their union therefore contains these three distinct elements only: \(A\cup B=\{1,2,3\}\). No element such as 4 or 6 can be added because it appears in neither set.
Frequently asked questions
What is the correct answer to this question?
\(\{1,2,3\}\)
Why is this the correct answer?
In a set, the order in which elements are written does not matter, and repeated elements are counted only once. Thus \(A\) and \(B\) contain exactly the same elements: 1, 2, and 3. Their union therefore contains these three distinct elements only: \(A\cup B=\{1,2,3\}\). No element such as 4 or 6 can be added because it appears in neither set.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Sets and their representations.
