Mathematics for IGCSE & O level - Sets (Section 3 - No. 48)
In a survey of 50 students, 20 like apples, 25 like bananas, and 10 like both. How many students like either apples or bananas?
35
40
45
50
คำอธิบาย
Use the inclusion-exclusion principle: n(A ∪ B) = n(A) + n(B) - n(A ∩ B). So, 20 + 25 - 10 = 35. Then the number of students are 35.