Question

There are 135 people in a sport centre.

73 people use the gym.
59 people use the swimming pool.
31 people use the track.
19 people use the gym and the pool.
9 people use the pool and the track.
16 people use the gym and the track.
4 people use all three facilities.
Given that a randomly selected person uses at least two facilities, what is the probability they
use all the facilities?

Answer 1

73:59:31:19:9:16:4
the probability of using 2 would be 8

Answer 2

1/9

Explanation:

4 people use all three facilities, then

16 - 4 = 12 people use the gym and the track and do not use the pool;

9 - 4 = 5 people use the pool and the track and do not use the gym;

19 - 4 = 15 people use the gym and the pool and do not use the track.

At least two facilities use 4 + 12 + 5 + 15 = 36 people, 4 of them use all three facilities. Thus, the probability that a randomly selected person which uses at least two facilities, uses all the facilities is 4/36 which is equivalent to 1/9