If n(A) = 10 and n(A ∩ B) = 4, what is n(A − B)?
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Answer and explanation
Correct answer: 6
The set A is divided into two disjoint parts: the elements common to A and B, represented by A ∩ B, and the elements of A outside B, represented by A − B. Thus n(A) = n(A ∩ B) + n(A − B). Substituting gives 10 = 4 + n(A − B), so n(A − B) = 6. Option C is correct.
Frequently asked questions
What is the correct answer to this question?
6
Why is this the correct answer?
The set A is divided into two disjoint parts: the elements common to A and B, represented by A ∩ B, and the elements of A outside B, represented by A − B. Thus n(A) = n(A ∩ B) + n(A − B). Substituting gives 10 = 4 + n(A − B), so n(A − B) = 6. Option C is correct.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Operations on Sets (Union, Intersection, Difference).
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