Question

There are three clubs at Redwood High School: Debate, Student council, and Key club. There are 1000 students in the school. And everyone is in at least one club.

• The total number of students in the debate club is 310
• The total number of students in the Student council is 650
• The total number who are in debate and student council is 170
• The total number of students who are in both debate and the key club are 150
• The total number of students who are in both student council and the key club is 180
• There are 50 students who are in all three clubs How many students are in the key club?

Answer 1

The number of students in the key club is 490

Explanation:

The given parameters are;

The number of student in the school = 1000

The total number of student in the debate club = 310

The total number of student in the student council = 650

The total number of student who are in debate and student council = 170

The total number of student who are in both debate and the key club = 150

The total number of student who are in both student council and the key club = 180

The number of students who are in all three clubs = 50

Therefore, we have;

Let A represent the number of students in the debate club

Let B represent the number of students in the student council

Let C represent the number of students in the key club

We have;

n(A∪B∪C) = n(A) + n(B) + n(C) - n(A∩B) - n(B∩C) - n(C∩A) + n(A∩B∩C)

Where;

n(A∪B∪C) = 1000

n(A) = 310

n(B) = 650

n(A∩B) = 170

n(B∩C) = 180

n(C∩A) = 150

n(A∩B∩C) = 50

Therefore;

n(C) = n(A∪B∪C) - (n(A) + n(B) - n(A∩B) - n(B∩C) - n(C∩A) + n(A∩B∩C))

Substituting the values gives;

n(C) = 1000 - (310 + 650 - 170 - 180 - 150 + 50) = 490

The number of students in the key club, n(C) = 490.