1. There is a section of river that needs to be dredged and dredged. At present, there are two dredging companies a and B. if company a does it alone for two days and company B does it alone for three days, it can just complete 25% of all the dredging tasks. If company a does it for four days first, the rest of the dredging work will be completed by company B alone, Then the time taken by company B is just 2 days more than that taken by company a to complete the dredging task alone? 2. A class organizes mountaineering activities. The students are divided into two groups: group A and group B. they march from the foot of the mountain along a road to the top of the mountain at the same time. The time ratio of group A and group B is 2:3 (1) Write directly the ratio of the speed of the two groups (2) When group a reaches the top of the mountain, group B goes to the mountainside a, and the distance from a to the top of the mountain is still 1.2 kilometers. How far is the distance from the foot of the mountain to the top of the mountain (3) On the basis of question (2), set group B to continue climbing from a, and group A to go down the mountain from the original road. The speed of going down the mountain is the same as that of going up the mountain, and meet group B at the hillside B. please put forward a corresponding question according to the above situation, Before giving answers (requirements: ① no other conditions shall be added to the raising of the question; ② the solution of the question must make use of all the known conditions provided by the above situation)

1. There is a section of river that needs to be dredged and dredged. At present, there are two dredging companies a and B. if company a does it alone for two days and company B does it alone for three days, it can just complete 25% of all the dredging tasks. If company a does it for four days first, the rest of the dredging work will be completed by company B alone, Then the time taken by company B is just 2 days more than that taken by company a to complete the dredging task alone? 2. A class organizes mountaineering activities. The students are divided into two groups: group A and group B. they march from the foot of the mountain along a road to the top of the mountain at the same time. The time ratio of group A and group B is 2:3 (1) Write directly the ratio of the speed of the two groups (2) When group a reaches the top of the mountain, group B goes to the mountainside a, and the distance from a to the top of the mountain is still 1.2 kilometers. How far is the distance from the foot of the mountain to the top of the mountain (3) On the basis of question (2), set group B to continue climbing from a, and group A to go down the mountain from the original road. The speed of going down the mountain is the same as that of going up the mountain, and meet group B at the hillside B. please put forward a corresponding question according to the above situation, Before giving answers (requirements: ① no other conditions shall be added to the raising of the question; ② the solution of the question must make use of all the known conditions provided by the above situation)

1. It takes X days for company a to complete the dredging task alone, and y days for company B to complete the dredging task alone (1 / x) * 2 + (1 / y) * 3 = 25% (1) (1 / x) * 4 + (1 / y) * (x + 2) = 1 (2) from (1) to get 2 / x + 3 / y = 0.25 (3) from (2) to get 4 / x + X / y + 2 / y = 1 (4) (3) * 2 - (4) (x + 2-6) / y = 0.5x-4 = 0.5yx = 4 + 0.5y

The three practical questions are correct, and they are added
1. A and B two workshops process a batch of the same parts. If a workshop processes 35 parts first, then B processes one day first, and then the workshop starts processing again, after five days, the number of parts processed by the two parts is equal. How many parts does B workshop process in one day?
2. Reduce one side of a square by 1 / 5 and increase the other side by 4 meters to get a rectangle. This rectangle is equal to the area of the original square. How many square meters is the square area?
3. Take seven yellow cattle and put them in the water buffalo group, then the number of the three groups of cattle is exactly the same. How many cows are there?

Second question:
Let the side length of the original square be X,
Then the square of x = = 0.8x (x + 4) 0.8, which is four fifths
The solution is x = 16
The square has an area of 256
Are you missing any conditions in the first question, but you can't understand the third one

Three calculation problems
(negative 5 and 2 / 3) + (negative 2.71)
(positive 19 and 1 / 8) + (negative 11 and 5 / 12)
(negative 10.5) + 22.3 + 12.5 + 7 / 20

1. Negative 8 and 113 out of 300
2.7 and 17 / 24
3.24.65