题目
题型:顺义区一模难度:来源:
3 |
4 |
2 |
3 |
(I)求该射手恰好命中两次的概率;
(II)求该射手的总得分X的分布列及数学期望EX;
(III)求该射手向甲靶射击比向乙靶射击多击中一次的概率.
答案
由题意知,P(B)=P(C)=
3 |
4 |
2 |
3 |
所以P(A)=P(BC
. |
D |
. |
C |
. |
B |
. |
D |
. |
C |
. |
B |
=
3 |
4 |
3 |
4 |
2 |
3 |
3 |
4 |
3 |
4 |
2 |
3 |
3 |
4 |
3 |
4 |
2 |
3 |
7 |
16 |
(II)根据题意,X的所有可能取值为0,1,2,3,4.
P(X=0)=P(
. |
B |
. |
C |
. |
D |
3 |
4 |
3 |
4 |
2 |
3 |
1 |
48 |
. |
C |
. |
D |
. |
B |
. |
D |
3 |
4 |
3 |
4 |
2 |
3 |
3 |
4 |
3 |
4 |
2 |
3 |
1 |
8 |
P(X=2)=P(BC
. |
D |
. |
B |
. |
C |
3 |
4 |
3 |
4 |
2 |
3 |
3 |
4 |
3 |
4 |
2 |
3 |
11 |
48 |
P(X=3)=P(B
. |
C |
. |
B |
3 |
4 |
3 |
4 |
2 |
3 |
3 |
4 |
3 |
4 |
2 |
3 |
1 |
4 |
P(X=4)=P(BCD)=
3 |
4 |
3 |
4 |
2 |
3 |
3 |
8 |
故X的分布列是