古典概型
1.恰有件次品的概率;
C(7,2)C(3,1)/C(10,3)
=21x3/120
=21/40
2.至少有件次品的概率(对立事件:没有次品)
1-C(3,7)/C(3,10)
=1-35/120
=1-7/24
=17/24