In a survey, n(U) = 80, n(A) = 45, n(B) = 37, and n(A ∩ B) = 18. How many students are in neither group?
Answer and explanation
Correct answer: 16
First calculate the number in at least one group: n(A ∪ B) = 45 + 37 − 18 = 64. Students in neither group are outside the union but still inside the universal set U. Hence, neither = n(U) − n(A ∪ B) = 80 − 64 = 16. Therefore, option A is correct; 64 is the number in at least one group, not the number outside both.
Frequently asked questions
What is the correct answer to this question?
16
Why is this the correct answer?
First calculate the number in at least one group: n(A ∪ B) = 45 + 37 − 18 = 64. Students in neither group are outside the union but still inside the universal set U. Hence, neither = n(U) − n(A ∪ B) = 80 − 64 = 16. Therefore, option A is correct; 64 is the number in at least one group, not the number outside both.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Venn Diagrams.