Answer: The required probability is 
Step-by-step explanation: Given that there are 52 white keys and 36 black keys on a standard piano. A person did not look and hit the keyboard twice.
We are find the probability that the person first hit a white key and hit a black key.
Let A and B represents the events that the person hit a white key and a black key respectively.
Then, the probabilities of events A and B are given by

Since the events A and B are independent of each other, so the probability that the person first hit a white key and hit a black key is given by

Thus, the required probability is 