Question

In a class of 25 students, 15 of them have a cat,

Answer 1

(I cannot draw the Venn diagram, sorry)

25 students in a class, 3 of them have neither -> Only 22 students have at least a pet.

15 of them have a cat, 16 of them have a dog -> There are 31 - 22 = 9 students that have both a cat and a dog


So, the probabilty of a person chosen at random that has a cat and a dog is 9 : 25 = 0.36 -> 36%.