P(A or B) represents the probability that a customer will buy either a mouse or a reptile at the pet store. So, there is a 20%, or 1 out 5 chance that a customer will buy either one when they come in to purchase a pet.
Step-by-step explanation:
Probability represents the fraction of the desired number of outcomes over the total number of outcomes. In the case of the pet store, their total outcomes can be the purchase of a mouse, reptile or bird. We don't know how much of each animal they have, however, they tell us that the probability that a customer will buy either a mouse OR a reptile is 0.20. This means that the probability of buying a mouse and the probability of buying a reptile are added together to equal 0.20 or 20% which is also 1/5.
