Events and Probability

Question

At central online high school, 45/100 of the students have a dog, 30/100 have a cat, and 18/100 have both a dog and a cat. 

What is the probability that a student who has a dog also has a cat?

Enter your answer as a reduced fraction with the / symbol, like this: 3/14

Answer 1

The probability of having a combination of 2 things is the product of having each one.

Since you have stipulated that the student has a dog, that probability is 1.

You are now looking for cat owners only among the group that owns dogs. The probability of your dog owner also being a cat owner is 18/45, which is 2/5.

Answer 2

part (18 kids with cats and dogs)

----

whole (45 kids with dogs)

reduces to 2/5