某城市為開發旅遊景點需要對古運河

㈣ 某城市為了緩解缺水狀況，實施了一項飲水工程，就是把200千米以外的的一條大河的水引到城市中來，把這個

設甲隊原計劃每天來修 x 千米源，乙隊原計劃每天修 y 千米。
按原計劃甲乙兩隊合作需要 50 天；
而實際甲隊共修了 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，
乙隊共修了 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；
可列方程組：
50(x+y) = 200 ，
30x+20(x+0.6)+30y+10(y+0.4) = 200 ；
解得：x = 2.4 ，y = 1.6 ，
即：甲隊原計劃每天修 2.4 千米，乙隊原計劃每天修 1.6 千米。

㈤ 假設你們班要去某個城市旅遊,請為你們班製作一份旅遊計劃，英語作文

下文僅供參考
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個旅遊景點，一位客人游覽這三個景點的概率分別是0.4，0.5，0.6，且客人是否游覽哪個

（1）分別記「客人游覽甲景點」、
「客人游覽乙景點」和「客人游覽丙景點」為版A₁，A₂，A₃，
由題設條件知權A₁，A₂，A₃相互獨立，
且P（A₁）=0.4，P（A₂）=0.5，P（A₃）=0.6，
則游覽兩個景點的概率為：
P（A₁?A₂?