Question

There are 130 people in a sport centre.

76 people use the gym.
60 people use the swimming pool.
32 people use the track.
23 people use the gym and the pool.
8 people use the pool and the track.
20 people use the gym and the track.
6 people use all three facilities.
A person is selected at random.
What is the probability that this person doesn't use any facility?

Answer 1

7/130

Explanation:

Using set notation to answer the question. let:

n(U) be the total people in a sport centre =130

n(G) be number of people that use the gym. = 76

n(P) be number of people that use the swimming pool. = 60

n(T) be number of people that use the track = 32

n(G∩P) be number of people that uses the gym and the pool = 23

n(P∩T) be number of people that uses the pool and the track = 8

n(G∩T) be number of people that uses the gym and the track = 320

n(G∩P∩T) be number of people that uses all three facilities = 6

Using the relationship below;

n(U)= n(GUPUT)+n(GUPUT)'

where n(GUPUT)' is the number of people that doesn't use any facility.

Before we can get that, we need to know n(GUPUT) using the formula;

n(GUPUT) = n(G) + n(P)+n(T)-n(G∩P)-n(P∩T)-n(G∩T)+n(G∩P∩T)

n(GUPUT) = 76+60+32-23-8-20+6

n(GUPUT) = 123

n(GUPUT)' = n(U)- n(GUPUT)

n(GUPUT)' = 130 - 123

n(GUPUT)' = 7

This means that 7 person doesn't use any facility.

Probability that a person selected at random doesn't use any facility = n(GUPUT)' /n(U) = 7/130