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问题 填空题
某次乒乓球比赛的决赛在甲乙两名选手之间举行，比赛采用五局三胜制，按以往比赛经验，甲胜乙的概率为
2
3
，记甲比赛的局数为X，则X的数学期望为______．
答案

根据题意题意，分析可得X可取的值为3，4，5；

当X=3时，分甲、乙胜两种情况；

即甲连胜三局，其概率为（

2
3
）3=
8
27
，乙连胜三局，其概率为（
1
3
）3=
1
27
，

则P（X=3）=

8+1
27
=
1
3
；

当X=4时，也分甲、乙胜两种情况；

若甲胜，其概率为[C32（

2
3
）2×
1
3
]×
2
3
=
8
27
，若乙胜，其概率为[C32（
1
3
）2×
2
3
]×
1
3
=
2
27
，

则P（X=4）=

8+2
27
=
10
27
；

当X=5时，也分甲、乙胜两种情况；

若甲胜，其概率为[C42（

2
3
）2×（
1
3
）2]×
2
3
=
16
81
，若乙胜，其概率为[C32（
1
3
）2×（
2
3
）2]×
1
3
=
8
81
，

则P（X=5）=

8
27
；

则X的数学期望EX=3×

1
3
+4×
10
27
+5×
8
27
=
107
27
；

故答案为：

107
27
．

阅读理解
阅读理解。
                                                  Holidays
                                                 Holiday News
     Vacancies (空位) now and in the school holidays at a country hotel in
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     For a few thousand pounds, all you've ever hoped for can be yours.
1. What can you do if you like to go on holidays with pets?
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C Join the World Sea Trip of 2008.
D. Visit Acapulco and Hawaii.
2. In what way is the Snowdonia Centre different from the other two holidays?
A. It provides chances of family gatherings.
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D. It offers comfortable room.
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A. food
B. rooms
C. body exercises
D. walking shoes
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单项选择题

治风寒感冒，咳嗽痰多，首选的药物是（）

A.羌活

B.柴胡

C.白芷

D.紫苏

E.香薷
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