某城市为开发旅游景点需要对古运河

㈣ 某城市为了缓解缺水状况，实施了一项饮水工程，就是把200千米以外的的一条大河的水引到城市中来，把这个

设甲队原计划每天来修 x 千米源，乙队原计划每天修 y 千米。
按原计划甲乙两队合作需要 50 天；
而实际甲队共修了 50 天，其中 30 天每天修 x 千米，另外 50-30 = 20 天每天修 x+0.6 千米，
乙队共修了 50-10 = 40 天，其中 30 天每天修 y 千米，另外 40-30 = 10 天每天修 y+0.4 千米；
可列方程组：
50(x+y) = 200 ，
30x+20(x+0.6)+30y+10(y+0.4) = 200 ；
解得：x = 2.4 ，y = 1.6 ，
即：甲队原计划每天修 2.4 千米，乙队原计划每天修 1.6 千米。

㈤ 假设你们班要去某个城市旅游,请为你们班制作一份旅游计划，英语作文

下文仅供参考
This month, I will travel to Changsha and Zhangjiajie with my two friends, which is supposed to be a seven-day trip. We will set out on 10th, June. Now, we have prepared many things, snacks and medicines included. Firstly, we will go to Changsha by plane. The tickets are cheap, so it’s a good choice to save time. We will stay there for two days. The main goal staying there is to enjoy the delicious food in Changsha. My friend has prepared a map of must-tries and I believe they must be good. Then we will go to Zhangjiajie by train. It’s not so far from Changsha, taking about five hours to get there. Zhangjiajie is famous for its wonderful mountains. The sceneries there are amazing that no one should miss. But we will have a tough journey for climbing high mountains, which is not easy for us all. This is why we will stay there for longer. In the end, we will go home by train. This is my plan for the journey. I am sure it will be a wonderful and fruitful journey.

㈥ 某城市有甲、乙、丙3个旅游景点，一位客人游览这三个景点的概率分别是0.4，0.5，0.6，且客人是否游览哪个

（1）分别记“客人游览甲景点”、
“客人游览乙景点”和“客人游览丙景点”为版A₁，A₂，A₃，
由题设条件知权A₁，A₂，A₃相互独立，
且P（A₁）=0.4，P（A₂）=0.5，P（A₃）=0.6，
则游览两个景点的概率为：
P（A₁?A₂?