(1)设“前两张卡片所标数字之和为偶数”为事件A,“第三张为奇数”为事件B,
则所求概率为P(B|A)=
=P(A?B) P(A)
=
C
+
A
A
A
C
A
A
.(6分)1 2
(2)ξ=1,2,3,4,则
P(ξ=1)=
=
A
A
;P(ξ=2)=2 5
=
A
A
A
;P(ξ=3)=3 10
=
A
A
A
;P(ξ=4)=1 5
=
A
A
A
.1 10
所以随机变量ξ的分布列为
ξ | 3 | 4 | 5 | 6 | ||||||
P |
|
|
|