名校
1 . 有三个盒子,每个盒子里有若干大小形状都相同的卡片.第一个盒子中有三张分别标号为
的卡片;第二个盒子中有五张分别标号为
的卡片;第三个盒子中有七张分别标号为
的卡片.现从每个盒子中随机抽取一张卡片,设从第
个盒子中取出的卡片的号码为
,则
为奇数的概率是( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/680e9ef551b325387ab31dca1f893705.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5969a26e4b3c149f694f857c655b08be.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a58f7fc045c0a8aec3aecaa6b287de84.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c05b9832b09731a574d4a4adf7448de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2243513b880087c89c0aa4f662a4af26.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/35bacde908aec2c313978fc4309d82bc.png)
A.![]() | B.![]() | C.![]() | D.![]() |
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名校
2 .
地发生地震时,相距
km的
两地都能感受到,已知
地位于A地的正东方向上,
地位于B地的东偏南
方向上,且
地距离
两地分别为
km和
km,则
的值是( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5c02bc0c74292b1e8f395f90935d3174.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/01c74a907dda6bb7d9d56d009d9df253.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8ac09dc1ca2cdd7aef28c218763d3e4d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/01c74a907dda6bb7d9d56d009d9df253.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4b2a3c02083c62d1e61edbc2eef8dfcd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/58bbb8c432c2b551b6515fcea5e1b742.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5c02bc0c74292b1e8f395f90935d3174.png)
A.![]() | B.![]() | C.![]() | D.![]() |
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3 . 小东同学参加一次答题活动,答题规则如下:本次答题共
道题,只有答对前
题,才能接下来答下一道题,答错题目,则答题结束;答对题目,则继续答下一题。若小东答题的准确率与题号成反比,且第一题的答题准确率
,小东至少答对两道题的准确率为( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5ca7d1107389675d32b56ec097464c14.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bdaa19de263700a15fcf213d64a8cd57.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5e5db9fa0bc36e2308bd3eecd5e78351.png)
A.![]() | B.![]() |
C.![]() | D.![]() |
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