概率论与数理统外 故得 P(A)=P(A)P(B)P(C)+P(A)P(B)P(C)+P(A)P(B)P(C) =0.4×0.5×0.3+0.6×0.5×0.3+0.6×0.5×0.7 =0.36. 因为A,=ABC+ABC+ABC, P(A )=P(ABC+ABC+ABC) =P(A)P(B)P(C)+P(A)P(B)P(C)+P(A)P(B)P(C) =0.41. ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) P A1  P A P B P C  P A P B P C  P A P B P C 故得  0.40.50.3  0.60.50.3  0.60.50.7  0.36. , 因为 A2  ABC  ABC  ABC  P(A)P(B)P(C) P(A)P(B)P(C) P(A)P(B)P(C)  0.41. ( ) ( ) 得 P A2  P ABC  ABC  ABC