Among 72 students, 34 like Mathematics, 31 like Physics, and 13 like both subjects. How many like neither subject?
Answer and explanation
Correct answer: 20
Let M be the set of students who like Mathematics and P the set who like Physics. By the inclusion–exclusion principle, n(M union P) = n(M) + n(P) − n(M intersection P) = 34 + 31 − 13 = 52. Therefore, the number who like neither subject is the total number minus the union: 72 − 52 = 20. Hence option B is correct.
Frequently asked questions
What is the correct answer to this question?
20
Why is this the correct answer?
Let M be the set of students who like Mathematics and P the set who like Physics. By the inclusion–exclusion principle, n(M union P) = n(M) + n(P) − n(M intersection P) = 34 + 31 − 13 = 52. Therefore, the number who like neither subject is the total number minus the union: 72 − 52 = 20. Hence option B is correct.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Venn Diagrams.