34% because every time you roll the dice each side has a probability of 17%, so since there are numbers 5 and 6 you want to roll, there is a 34% you will get those numbers. the first roll doesn't have an affect on your next roll
Ok, if you roll the dice once - you'll get: 1, 2, 3, 4, 5 or 6. If you roll it twice, you can get one of these combinations: 1,1 - 1,2 - 1,3 - 1,4 - 1,5 - 1,6 2,1 - 2,2 - 2,3 - 2,4 - 2,5 - 2,6 3,1 - 3,2 - 3,3 - 3,4 - 3,5 - 3,6 4,1 - 4,2 - 4,3 - 4,4 - 4,5 - 4,6 5,1 - 5,2 - 5,3 - 5,4 - 5,5 - 5,6 6,1 - 6,2 - 6,3 - 6,4 - 6,5 - 6,6 Here there are 36 combinations in total. Your chance of getting a 5 and a 2 is 1/36. 5,2 only appears once in this list of possible combinations. 2,5 doesn't count (as 2 would come up first).
For margin of error to be a maximum of 3: 3 = z*(SD / sqrt(n)), where z is the z-score, SD is the standard deviation and n is the sample size. z = 1.96 for a 95% confidence interval, and we are given SD = 15. 3 = 1.96*15/sqrt(n) sqrt(n) = 9.8 n = 96.04 ~ 96 commercials.