Question Detail
Question
If n(A) = 20, n(A ∪ B) = 15, and n(A ∩ B) = 5, find n(B).
Correct Answer
Option D is the correct answer.
Detailed Explanation
Using the formula n(A ∪ B) = n(A) + n(B) − n(A ∩ B), substitute values: 15 = 20 + n(B) − 5. Simplifying gives 15 = 15 + n(B), so n(B) = 0.
Hint
Substitute the given values into n(A ∪ B) = n(A) + n(B) − n(A ∩ B) and solve for n(B).