Three standard fair 6-sided dice are rolled. What is the expected number of 6's rolled? (For example, if two 6's and a 5 are rolled, then the answer is 2.)
Probability of exactly one six: p1 = (1/6)*(5/6)^2*3
Probability of exactly two sixes: p2 = (1/6)^2*(5/6)*3
Probwbility of exactly three sixes: p3 = (1/6)^3
Expected number of sixes: 1*p1 + 2*p2 + 3*p3
