Jack rolls 5 fair six-sided dice. What is the probability that at least two dice show a 6?
6 are rolled. Probability of getting 6 is 1/6. We need at least 2. 1/6*1/6 but there are four left. We don't necessarily need 6 for these leftover 4 dice so that would by 5/6*5/6*5/6*5/6. Combining this with 1/6*1/6, that would be 1/6*1/6*5/6*5/6*5/6*5.6 which is equivalent to 0.01339591906.
Complementary counting
Case 1: No dice show 6
5^5/6^5
Case 2: One die shows a 6
1/6 * 5^4/6^4 = 5^4/6^5
Add them up to get 4026/6^5 = 671/1296