In a class, n(A) = 74, n(B) = 68, and 86 students are in exactly one set. What is n(A ∩ B)?
Answer and explanation
Correct answer: 28
Let x = n(A ∩ B). The students in exactly one set are those in A only or B only. Their number is [n(A) − x] + [n(B) − x] = n(A) + n(B) − 2x. Therefore, 86 = 74 + 68 − 2x = 142 − 2x. Thus 2x = 56 and x = 28. Hence, the intersection contains 28 students, so option C is correct.
Frequently asked questions
What is the correct answer to this question?
28
Why is this the correct answer?
Let x = n(A ∩ B). The students in exactly one set are those in A only or B only. Their number is [n(A) − x] + [n(B) − x] = n(A) + n(B) − 2x. Therefore, 86 = 74 + 68 − 2x = 142 − 2x. Thus 2x = 56 and x = 28. Hence, the intersection contains 28 students, so option C is correct.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Venn Diagrams.