Final answer:
The probability that a randomly selected household owns either a dog, a cat, or both is 54%, calculated by adding the probabilities of owning a dog and a cat and subtracting the intersection of both.
Step-by-step explanation:
The probability that a household owns a dog or a cat can be calculated using the formula for the probability of the union of two events, which accounts for the fact that some households may own both a dog and a cat. To find the probability of a dog or a cat (or both), we add the probability of owning a dog to the probability of owning a cat and subtract the probability of owning both, since these households have been counted twice.
P(Dog or Cat) = P(Dog) + P(Cat) - P(Dog and Cat)
P(Dog or Cat) = 40% + 32% - 18%
P(Dog or Cat) = 54%
Thus, the probability that a randomly selected household owns either a dog, a cat, or both is 54%.