Three teachers, A, B and C, guide five students. Each teacher guides at least one teacher, and only one is the biggest! 1 ~ A guidance ...
1, the probability that teacher A instructs each student is the same, which is1/5;
2、c 1/5(C2/4+C3/4)/[c 1/5(c 1/4+C2/4+C3/4)]= 5( 12+4)/[5(4+ 12+4)]= 4/5；
3. Probability 1: 1/5, 2: 3/5, 3:1/5;
The expectation is: e =1x1/5+2x3/5+3x1/5 = 2.