Question

A fair six sided dice has the faces numbered from 1 to 6. The dice is thrown 4 time. Calculate the probability of exactly 2 fives. the answer is 25/216

Answer 1

prob(5) = 1/6
prob(not 5) = 5/6

you want 5 twice, not5 2 twice

prob = C(4,2) (1/6)^2 (5/6)^2
= 6(1/36)(25/36) = 25/216