If n(A ∪ B ∪ C) = 140, exactly one set has 65 elements and exactly two sets have 51 elements, what is n(A ∩ B ∩ C)?
Answer and explanation
Correct answer: 24
The union is partitioned into three mutually exclusive types of Venn regions: elements belonging to exactly one set, elements belonging to exactly two sets, and elements belonging to all three sets. Thus 140 = 65 + 51 + n(A ∩ B ∩ C). Solving gives n(A ∩ B ∩ C) = 140 − 116 = 24. Therefore option A is correct.
Frequently asked questions
What is the correct answer to this question?
24
Why is this the correct answer?
The union is partitioned into three mutually exclusive types of Venn regions: elements belonging to exactly one set, elements belonging to exactly two sets, and elements belonging to all three sets. Thus 140 = 65 + 51 + n(A ∩ B ∩ C). Solving gives n(A ∩ B ∩ C) = 140 − 116 = 24. Therefore option A is correct.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Venn Diagrams.