Final answer:
The probability of getting heads and then rolling a multiple of 3 is 1/6.
Step-by-step explanation:
The probability of getting heads and then rolling a multiple of 3 can be found by multiplying the probabilities of getting heads and rolling a multiple of 3 separately.
The probability of getting heads is 1/2, since there are two sides on a coin - heads and tails, and they are equally likely to occur.
The probability of rolling a multiple of 3 on a fair number cube is 2/6, since there are two numbers (3 and 6) that are multiples of 3 out of the six possible outcomes (1, 2, 3, 4, 5, 6).
Therefore, the probability of getting heads and then rolling a multiple of 3 is (1/2) * (2/6) = 1/6.