Two fair coins are tossed together. What is the probability of getting one head and one tail? Give the probability as a fraction out of the four equally likely outcomes.

Explication

Among the four pairs, heads-tails and tails-heads both give one head and one tail, so two of the four cases succeed. Answering 1/3 comes from listing two heads, two tails and one of each as though they were three equally likely results, but the mixed result arises in two ways and so occurs twice as often as either matching pair.