Answer:
1/3 or 0.333
Step-by-step explanation:
If we know that exactly 2 of the 6 rolls resulted in a 1. Then the number of ways to arrange the two 1s into 6 slots is
ways
Of these 15 ways, some of them have 1 at the 1 slot.
The number of ways to arrange the two 1s so that one 1 is in the 1st slot is 5. Because the 2nd 1 is in any of the other 5 slots.
Therefore, the probability that the first roll resulted in a 1,given that exactly two of the six rolls resulted in a 1 is
5 / 15 = 1/3 or 0.333