If A = {1, 2, 3, 4} and B = {3, 4, 5, 6}, what is (A ∪ B) − A?
Answer and explanation
Correct answer: {5, 6}
First form the union: A ∪ B = {1, 2, 3, 4, 5, 6}. The difference (A ∪ B) − A means that every element belonging to A must be removed from the union. Removing 1, 2, 3, and 4 leaves {5, 6}. This also follows from the identity (A ∪ B) − A = B − A. The elements 3 and 4 are not retained because they are already in A.
Frequently asked questions
What is the correct answer to this question?
{5, 6}
Why is this the correct answer?
First form the union: A ∪ B = {1, 2, 3, 4, 5, 6}. The difference (A ∪ B) − A means that every element belonging to A must be removed from the union. Removing 1, 2, 3, and 4 leaves {5, 6}. This also follows from the identity (A ∪ B) − A = B − A. The elements 3 and 4 are not retained because they are already in A.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Operations on Sets (Union, Intersection, Difference).
