What is the probability that at least two of the faces match when you roll four fair six-sided dice? Express your answer as a common fraction.
Easier to first caculate the probability that no faces match =
[(6) (5) (4) (3) ] / 6^4 = 360 / 1296 = 5/18
So the probability that at least two faces match = 1 - 5/18 = 13 / 18
