1 . 为了让观赏游玩更便捷舒适,常州恐龙园推出了代步工具租用服务.已知有脚踏自行车
与电动自行车
两种车型,采用分段计费的方式租用.
型车每
分钟收费
元(不足
分钟的部分按
分钟计算),
型车每
分钟收费
元(不足
分钟的部分按
分钟计算),现有甲乙丙丁四人,分别相互独立地到租车点租车骑行(各租一车一次),设甲乙丙丁不超过
分钟还车的概率分别为
,并且四个人每人租车都不会超过
分钟,甲乙丙均租用
型车,丁租用
型车.
(1)求甲乙丙丁四人所付的费用之和为25元的概率;
(2)求甲乙丙三人所付的费用之和等于丁所付的费用的概率;
(3)设甲乙丙丁四人所付费用之和为随机变量
,求
的概率分布和数学期望.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f9e8449aad35c5d840a3395ea86df6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b53c7539ed297ea63b9ace6f5cc58ca8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d91e07104b699c4012be2d26160976a2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b53c7539ed297ea63b9ace6f5cc58ca8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b53c7539ed297ea63b9ace6f5cc58ca8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f9e8449aad35c5d840a3395ea86df6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b53c7539ed297ea63b9ace6f5cc58ca8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d07ae0b4264da6a8812454ffd2f20d94.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b53c7539ed297ea63b9ace6f5cc58ca8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b53c7539ed297ea63b9ace6f5cc58ca8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b53c7539ed297ea63b9ace6f5cc58ca8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7a2d050db82b7dc4171561b1a2658fcd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3b3779b4ea5477aebfe85113b0de1d60.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f9e8449aad35c5d840a3395ea86df6d.png)
(1)求甲乙丙丁四人所付的费用之和为25元的概率;
(2)求甲乙丙三人所付的费用之和等于丁所付的费用的概率;
(3)设甲乙丙丁四人所付费用之和为随机变量
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5b734e8f1546481e3eb4976008a045de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5b734e8f1546481e3eb4976008a045de.png)
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