It s been 25 miles to build a road, and there s 400 meters left, how long is this road?

400 can be calculated like this.

In the exam, I always see that some students have many gaps in the test papers, that is, there are several questions that are not done at all. Of course, as the saying goes, if you are bold, you will not be bold. But it's one thing to not be able to do it, and it's another thing not to do it.

The solution and result of a slightly more difficult math problem cannot be seen at a glance. It is necessary to analyze, explore, compare, draw, write and calculate, and only after twists and turns of reasoning or calculation can a certain connection between the conditions and the conclusion be revealed, and the whole idea will become clear and clear.

When solving the specific problem, we must carefully examine the problem, firmly grasp all the conditions of the question, and do not ignore any of the conditions. There is a certain commonality between a question and a class of questions, you can think about the general idea and general solution of this type of question, but it is more important to grasp the particularity of this question, and grasp the difference between this question and this type of question. Mathematics problems are almost not the same, and there are always one or several conditions that are different, so the thinking and problem-solving process are also different.

Some students and teachers will do the questions they have taught, but they will not do other questions, they will only draw the scoop in the same way, and they will stare at the problem if there are some small changes in the question, and they don't know where to start.

There is no limit to the number of mathematical problems, but there are limits to the ideas and methods of mathematics. As long as we have learned the relevant basic knowledge and mastered the necessary mathematical ideas and methods, we will be able to deal with the infinite problems smoothly. The more questions you do, the better, and the sea of questions is endless, and you can't finish them.

The key is whether you have developed good mathematical thinking habits and whether you have mastered the correct mathematical problem solving methods.

Solving problems requires a wealth of knowledge and more importantly, self-confidence. If you don't have self-confidence, you will be afraid of difficulties and give up; Only with self-confidence can we move forward bravely, not give up easily, redouble our efforts to study, and hope to overcome difficulties and usher in our own spring.

1050 meters. According to the meaning of the destruction chain, it can be obtained: the length of the road is x, x (1-60%)=420, and x=1050 meters, so the road length is 1050 meters.

400-400=1000-400,=600 (m) Answer: There are 600 meters left in the cherry blossom source

Analysis: If it is 400 meters, the total length of this road is 400 meters, so how many meters are left by subtracting the repaired from the total length

Comments: First of all, according to the meaning of fraction division, grinding pure to find the full length is the key to completing this problem

3600 (m).

Answer: It is also learned that the remaining 3,600 meters of wild liquid have not been repaired.

Summary. 1 kilometer has been repaired by 30%, and I multiply 1,000 by 30%, which is equal to 1,000 meters.

The construction of a 1-kilometer road has been repaired by 35% of how many meters have been repaired.

1 kilometer has been repaired by 30%, and I multiply 1,000 by 30%, which is equal to 1,000 meters.

1 kilometer has been repaired by 35%, and I will multiply 1,000 by 35%, which is equal to 1,000 meters.

Expand. The distance repaired is the total distance, multiplied by the percentage repaired.

There are still 45% left that have not been repaired, and according to the total length of the noise minus the length of the repaired dust hole, it is concluded that there are still 180 thousand pai touching dry rice left that have not been repaired, and then 180 400x100% = 45%.