£ represents a group of 30 people that visited paris for a weekend break. 13 of the group visited the eiffel tower (ET) 16 of the group visited the no tre-dame cathedral (NDC) 7 of the group did not visit either of these places a person is chosen at random from the group. what is the probability that this person only visited one of the two places?

for selecting a person at random, the probability that this person only visited one of the two places is equal to the number of persons that visited only one place divided the total amount of persons.

First, calculate the number of persons that visited only one place.

let's take the initial data and sum it all.

13 + 16 = 29 persons that visited at least one place.

7 persons that not visited any of the places.

29 + 7 = 36

But in the group, we have 30 persons, so here we had a surplus of 6 persons.

This means that 6 persons visited the two places, so we must discard those 6 in both groups,

People that only visited the Eiffel Tower 13 + 6 = 7

People that only visited the Cathedral 16 - 6 = 10

total: 10 + 7 = 17

proportion = 17/30 = 0.56

Then, the probability that a selected a random person only visited one of the two places is 0.56 or 56%