1 未检查出次品概率=0.35+0.25*C(49,10)/C(50,10)+0.2*C(48,10)/C(50,10)+0.18*C(47,10)/C(50,10)+0.02*C(46,10)/C(50,10)
=0.35+0.25*40/50+0.2*40*39/50*49+0.18*40*39*38/50*49*48+0.02*40*39*38*37/50*49*48*47
=0.35+0.2+0.1273+0.091+0.008
=0.776
2 已知未查出次品 确定无次品概率=0.35/0.776=0.451=45.1%