Question Detail
Question
Out of 400 students in a International school UNILAG, 300 are offering Biology and 190 are offering Chemistry. How many students are offering both subjects if 70 students are offering neither subject?
Correct Answer
Option D is the correct answer.
Detailed Explanation
Total students = 400. Those offering at least one = 400 - 70 = 330. Using inclusion-exclusion: n(B ∪ C) = n(B) + n(C) - n(B ∩ C) ⇒ 330 = 300 + 190 - x ⇒ 330 = 490 - x ⇒ x = 160.
Hint
First find number who offer at least one subject, then use n(A ∪ B) = n(A) + n(B) - n(A ∩ B).