1 . 数学建模是从定量的角度分析和研究一个实际问题,需要在深入调查研究、了解对象信息、作出简化假设、分析内在规律等工作的基础上;用数学的符号和语言作表述来建立数学模型,再对数学模型来进行求解,然后根据结果去解决实际问题.某校为组建数学建模小组需要在甲、乙两个班级通过考试选拔组员,甲、乙两个班各有10名同学参加,设甲、乙两班的数据分别为
,
,…,
和
,
,…,
,他们的考试成绩如下表:
(1)现从考试成绩不低于90分的同学中随机抽取两名同学成绩,求至少有一个来自甲班的概率;
(2)已知
,求
的值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c814128ea2139e33db94ea590e7c2223.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/aec19b68e3add9d5bfcc6269a1855b87.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5ab84c3fe70da38ccb246fd4a71f9d86.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54015ff5b49e3283901da1291b6b921d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/46f6872ffb1934339c53c2c2282d5889.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9a1c1904afc801069716e5dca11f51e7.png)
甲班 | ![]() | ![]() | ![]() | ![]() | ![]() | ![]() | ![]() | ![]() | ![]() | ![]() |
82 | 73 | 69 | 81 | 92 | 72 | 86 | 91 | 78 | 83 | |
乙班 | ![]() | ![]() | ![]() | ![]() | ![]() | ![]() | ![]() | ![]() | ![]() | ![]() |
95 | 76 | 96 | 91 | 85 | 90 | 81 | 78 | 98 | 86 |
(2)已知
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a8321ce23741a21c4a1f6cd22b30aaa5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2408f2a4f169704fc8626661dd6968a3.png)
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