In a survey of 150 people, 85 like tea, 70 like coffee, and 40 like both tea and coffee. How many people like neither tea nor coffee?
Answer and explanation
Correct answer: 35
Let T be the set of people who like tea and C be the set of people who like coffee. By inclusion–exclusion, n(T ∪ C) = n(T) + n(C) − n(T ∩ C) = 85 + 70 − 40 = 115. Therefore, the number who like neither is the complement of T ∪ C in the survey: 150 − 115 = 35. Hence, option A is correct.
Frequently asked questions
What is the correct answer to this question?
35
Why is this the correct answer?
Let T be the set of people who like tea and C be the set of people who like coffee. By inclusion–exclusion, n(T ∪ C) = n(T) + n(C) − n(T ∩ C) = 85 + 70 − 40 = 115. Therefore, the number who like neither is the complement of T ∪ C in the survey: 150 − 115 = 35. Hence, option A is correct.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Complement of a Set and Its Properties.