Question

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

16 of them have a dog and 3 of them have neither.
Find the probability that a student chosen at random
has a cat and a dog.

Answer 1

number of students who have cat and dog

= y

= 9

P( student chosen has a dog and cat )

= 9/25

Answer 2

So 3 have no pets, so 25 - 3 = 22 students have a pet.

There are 15 cats and 16 dogs so 15 + 16 = 31.

And then 31 - 22 = 9. The 9 means that 9 students have both pets.

So the probability is 9/25.