probability一問

你條問題有點兒不清晰，我有兩個答案
Ans.1
如果問題係問三粒加埋係1,probability 係0
因為冇可能出現
Ans.2
三粒至少有一個1,probability 係91/216
Steps:
probability
=(1/6x5/6x5/6)+(5/6x1/6x5/6)(5/6x5/6x1/6)(1/6x1/6x5/6)
(1/6x5/6x1/6)(5/6x1/6x1/6)(1/6x1/6x1/6)
=91/216