For three sets, n(A) = 90, n(B) = 84, n(C) = 78, n(A ∩ B) = 36, n(B ∩ C) = 32, n(C ∩ A) = 30, and n(A ∩ B ∩ C) = 13. What is n(A ∪ B ∪ C)?
Answer and explanation
Correct answer: 167
Apply the inclusion-exclusion formula for three sets: n(A ∪ B ∪ C) = n(A) + n(B) + n(C) − n(A ∩ B) − n(B ∩ C) − n(C ∩ A) + n(A ∩ B ∩ C). Substitution gives 90 + 84 + 78 − 36 − 32 − 30 + 13 = 167. The triple intersection is added once at the end because it was subtracted too many times. Thus option B is correct.
Frequently asked questions
What is the correct answer to this question?
167
Why is this the correct answer?
Apply the inclusion-exclusion formula for three sets: n(A ∪ B ∪ C) = n(A) + n(B) + n(C) − n(A ∩ B) − n(B ∩ C) − n(C ∩ A) + n(A ∩ B ∩ C). Substitution gives 90 + 84 + 78 − 36 − 32 − 30 + 13 = 167. The triple intersection is added once at the end because it was subtracted too many times. Thus option B is correct.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Venn Diagrams.