Answer: The required probability is

Step-by-step explanation: We are given that a six-sided number cube is rolled.
We are to find the probability of getting a 2 and then a 1, given that the first number rolled was 2.
Let S denotes the sample space of rolling a six-sided cube, A be the event of rolling a 2 and B be the event of rolling a 1.
Then,
n(S) = 6, n(A) = 1 and n(B) = 1.
Now, the probabilities of events A and B :

Since the two events A and B are independent of each other, so the required probability is given by

Thus, the required probability is
