摘要: The best title for the passage is “ . Reaching the Top of the Mountain B. Standing at the Top of the Mountain Conversations between Father and Son D. How to Get to the Top of the Mountain C If you travel by air across the center of Africa or South America, you fly over forests for thousands of kilometers. These great forests are the oceans of trees. They are full of thousands and thousands of different kinds of plants and animals. However, the world forests are getting smaller all the time. We are cutting down the trees because we need wood, and we need more farmland. Some people say that there will not be any forests like these in 20 or 30 years. What will happen if they disappear? If we cut down our forests, a lot of plants and animals will disappear from the world. In a lot of places the new farmland will soon look like the old deserts. Crops will not grow there. It will not rain very often, and the weather will get very hot. Perhaps the climate of the world will change. This will be dangerous for everyone in the world. That is why we must take care of forests.
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某校设计了一个实验学科的实验考查:考生从6道备选题中一次性随机抽取3道题,按照题目要求独立完成全部实验操作.规定:至少正确完成其中2题的便可通过考查.已知6道备选题中,考生甲有4道题能正确完成,2道题不能完成;考生乙每题正确完成的概率都是
,且每题正确完成与否互不影响.
(Ⅰ)求考生甲通过实验考查的概率;
(Ⅱ)求乙考生至少正确完成2道题的概率. 查看习题详情和答案>>
| 2 | 3 |
(Ⅰ)求考生甲通过实验考查的概率;
(Ⅱ)求乙考生至少正确完成2道题的概率. 查看习题详情和答案>>
2010年11月广州成功举办了第十六届亚运会.在华南理工大学学生会举行的亚运知识有奖问答比赛中,甲、乙、丙同时回答一道有关亚运知识的问题,已知甲回答对这道题目的概率是
,甲、丙两人都回答错的概率是
,乙、丙两人都回答对的概率是
.
(1)求乙、丙两人各自回答对这道题目的概率.
(2)求回答对这道题目的人数的随机变量ξ的分布列和期望.
查看习题详情和答案>>
| 3 |
| 4 |
| 1 |
| 12 |
| 1 |
| 4 |
(1)求乙、丙两人各自回答对这道题目的概率.
(2)求回答对这道题目的人数的随机变量ξ的分布列和期望.
某问答游戏的规则是:共5道选择题,基础分为50分,每答错一道题扣10分,答对不扣分.试分别用列表法、图象法、解析法表示一个参与者的得分y与答错题目道数x(x∈{0,1,2,3,4,5})之间的函数关系.
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