You are right, they are comman things, 10m included in 1h,

来源: 于 2011-01-30 20:59:44 [旧帖] [给我悄悄话] 本文已被阅读：次

We have P(E)<=P(F),if E is subset of F. So,Bu's answer is not right. But I can construct a Q let his answer almost is right.There are 6 period,every period one star shows up,seen by a man, the prob. is the same,the Prob. seen all stars by man is .9,What is the Prob. a star seen by man in the first period?

The answer is .98...near to 1-.1(1/6).