Final answer:
The probability of rolling a sum of 8 with two dice, when the first die shows a 4, is 1/6.
Step-by-step explanation:
When you roll 2 dice and the first die is a 4, the probability that the sum of the two dice is exactly 8 can be calculated by looking at the possible outcomes of the second die.
There is only one outcome that will give us a sum of 8 when the first die is a 4, which is rolling a 4 on the second die (4+4=8).
With a fair six-sided die, the probability of rolling any given number is 1/6.
Therefore, the probability that the sum of the two dice is exactly 8, given that the first die is a 4, is 1/6. This is the only outcome (rolling a 4 on the second die) that will satisfy the condition out of the 6 possible outcomes of rolling the second die.