If n(A) = 45, n(B) = 38, and only A has 19 elements, that is, n(A − B) = 19, what is n(A ∩ B)?
Answer and explanation
Correct answer: 26
Set A is divided into two disjoint parts: the elements only in A, represented by A − B, and the elements common to A and B, represented by A ∩ B. Therefore n(A) = n(A − B) + n(A ∩ B). Using the given values, 45 = 19 + n(A ∩ B), so n(A ∩ B) = 45 − 19 = 26. Hence option B is the only correct answer.
Frequently asked questions
What is the correct answer to this question?
26
Why is this the correct answer?
Set A is divided into two disjoint parts: the elements only in A, represented by A − B, and the elements common to A and B, represented by A ∩ B. Therefore n(A) = n(A − B) + n(A ∩ B). Using the given values, 45 = 19 + n(A ∩ B), so n(A ∩ B) = 45 − 19 = 26. Hence option B is the only correct answer.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Operations on Sets (Union, Intersection, Difference).