Problem 4
Part A:
To calculate the probability of rolling a red on the first roll, you just have to calculate the probability of rolling a red on a given die and multiply it by the probability of picking that die. To get the final probability, just sum up the individual probabilities.
Part B:
The most important thing to remember while doing this part is that when you calculate the probability of rolling a red on the second roll given that the first roll is a red, you have to take into account the probability of rolling a red on the second try and the first try of a given die as well as the probability of picking that die.
