1. The problem statement, all variables and given/known data What is the probability of rolling exactly two ones from a set of six dice? 2. Relevant equations Binomial probability distribution? 3. The attempt at a solution I tried: P = 6!/(2! x 4!) x (1/6)^2 x (5/6)^4 and got 0.20, but the book says that's a factor of 10 too high!