The distance between a and B is 24 km. The fast and slow trains are both from a to B. when the fast train leaves, the slow train has already run for 4 km. When the fast train arrives at B, the slow train is 2 km away from B. how far is the fast train from B to catch up with the slow train? When the fast train runs 24 km, the slow train actually runs 24-4-2 = 18 (km), that is, the fast train runs 6 (km) more than the slow train. After that, I don't know how to do it,

The express train runs 24 kilometers, while the local train actually runs:
24-4-2 = 18 km
That is to say, the fast train takes 24 km, 24-18 km more than the slow train
The fast train overtakes the local train by 4 kilometers
So when the express train catches up with the local train, OK:
4 / 6 × 24 = 16 km
24-16 km away from Yidi

A total of 10 questions in a test, 5 points for one right, 2 points for one wrong, and 36 points for Xiaoqiang

5 points for one right question and 2 points for one wrong question (which can be regarded as - 2 points). If all 10 right questions are 50 points, 5 + (- 2 points) = 7 points for each wrong question on the basis of 50 points
Got 36, 50-36 = 14, 14 / 7 = 2
To put it simply, consider how many points you get for doing everything right, and then subtract 7 points for each mistake

Will Arctic glaciers melt and sea levels rise?
According to the principle of buoyancy, we know that there is a piece of floating ice in a glass of water. When all the ice melts, the water surface will not rise or fall. So why do we say that melting glaciers in the Arctic will lead to sea level rise?

After the Arctic ice melts, the sea level will not rise, because the Arctic ice is floating on the sea. But the Antarctic ice is different. The Antarctic ice is land ice, and the Antarctic ice is much more than the Arctic ice. Therefore, if the Antarctic and Greenland ice melt completely, the sea level will certainly rise. It is said that the sea level will rise more than 60 meters

This year, my grandfather's age is six times that of Xiao Ming. In a few years, my grandfather's age will be five times that of Xiao Ming. In a few years, my grandfather's age will be four times that of Xiao Ming

Suppose grandfather is x years old, then Xiao Ming is y years old. The first year passed a, and the second year passed B, x = 6yx + a = 5 (y + a) x = 5Y + 4ax + A + B = 4 (y + A + b) x = 4Y + 3A + 3b solution x = 24a, y = 4A, B = 5A3 according to the actual a = 3, B = 5Y = 12x = 72 A: grandfather is 72 years old

Geography. Which is the greater distance between the sea level of the two poles and that of the equator?
If not, how should we understand the altitude of the terrain?

The equator is big, the earth is a slightly flat sphere with two poles. The altitude is also called absolute altitude, which is the height difference between a certain place and sea level. It is usually calculated according to the average sea level. It is the vertical distance above the sea level of a certain place on the ground. The starting point of altitude is called altitude zero or leveling zero, which is the average sea water of a certain coastal place

1. For a project, it takes 12 days for Party A to complete it alone, and 9 days for Party B to complete it alone. If Party A does it first for several days, and Party B continues to do it, it takes 10 days to complete it. How many days did party a do it?
2. For a job, Party A completes 1 / 4 of all the work in 5 hours, and Party B completes the remaining half of the task in 6 hours. Finally, Party A and Party B cooperate in the remaining part. How many hours will it take?
3. For a project, it takes 12 hours for Party A to do it alone and 18 hours for Party B to do it alone How many hours do you share to complete the task?
4. For a project, team a completed it in 24 days, team B completed it in 30 days, team a and team B cooperated for 8 days, and team C completed the rest in 6 days?
5. For a project, team a did it alone for 20 days and team B did it alone for 30 days. Now they are doing it together. During this period, team a rested for 3 days and team B rested for several days. It took 16 days from the beginning to the completion. How many days did team B rest?
6. To build a section of highway, it takes 40 days for team a to do it alone, and 24 days for team B to do it alone. Now the two teams start work from both ends at the same time, and they meet at 750 meters from the midpoint. How long is this section of highway?
7. For a project, the cooperation between team a and team B takes 12 days to complete, the cooperation between team B and team C takes 15 days to complete, and the cooperation between team a and team C takes 20 days to complete?
8. A batch of parts can be processed within 24 days through the cooperation of Party A and Party B. now, Party A will do it for 16 days first, and then Party B will do it for 12 days. Two fifths of these parts are left unfinished. It is known that Party A processes 3 more parts than Party B every day. How many parts are there in this batch?

Question 1: 4 days. Question 2.10/3 hours. Question 3.14 and 1 / 3 hours. Question 4.10 days. Question 5.5.5 days
6000 meters, 7.23.5 days and 8.360 questions
Write the process yourself

In the section of atmospheric circulation in geography textbook for senior one, there are two sea level isobaric maps. Why is the global isobaric map only called sea level map? Why is the land isobaric map also called sea level map

The English expression of sea-level pressure chart is surface pressure. If surface pressure is translated literally, it means surface pressure. But what is the surface? The surface pressure of Mount Everest is only more than 300 HPA, which is only more than 30% of the sea surface pressure of 1000 HPA. At present, the central sea-level pressure of the strongest typhoon tip is 870 HPA, The surface pressure of Mt. Everest is much higher than that of Mt. Everest at 300hPa, but can they be directly compared? Obviously not. So people think of a method to convert all the pressure measured on the surface of the earth at different altitudes to the pressure at sea level through certain methods, which is called sea surface pressure
The specific conversion method is commonly known as the static equilibrium method. You must remember the liquid pressure formula in hydrostatics, P = a × g × h, a is the density of the liquid. If we measure the pressure at a certain depth of the ocean with a manometer, it is 1000000pa, Then we can know immediately that the pressure at 1m from this position is 1000000 + 1000 × 9.8 × 1 = 1009800pa. The same is true in the atmosphere, except that the density of the atmosphere on the earth's surface is about 1.29kg/m3. If the pressure measured on the earth's surface is 101300pa (1013hpa), then the pressure above 1m is 101300-1.29 × 9.8 × 1 = 101287pa = 1012.87hpa, On the contrary, sea-level pressure can also be obtained from the pressure above 1m. However, there is one difference between the atmosphere and the ocean, that is, the density of sea water is usually around 1000km / m3, and the density of the atmosphere often changes because of its good compressibility. For example, the atmospheric density in the tip center is only 85% of the average density of sea-level atmosphere of 1.29kg/m3, so that the sea level rises 1m in the tip center, The pressure change is only 10.7 Pa. the height change of 1 m on Mt. Everest, and the pressure change is much smaller. So the question comes. If the pressure measured by the weather station on Mt. Huangshan is 850 hPa, can we accurately tell the pressure at the foot of Mt. Huangshan? Unfortunately, we can only approximate a density value, and then approximate the pressure at the foot of Mt. Huangshan according to the fluid pressure equation, because it is approximate, So there will be errors. The height of Huangshan Mountain is only 1800 meters, and the error is acceptable. However, if it is the Qinghai Tibet Plateau, the error will be large. Therefore, we often see strong high pressure or low pressure in the Qinghai Tibet Plateau. The calibration of the central pressure of the cold high pressure is often different, which is also the reason. The center of the cold air is often located in the Mongolian Plateau with a height of about 3000m, Are there different methods for estimating sea level pressure^_^
Through the above method, the pressure data measured by thousands of weather stations in the world can be unified to the sea level, so the global isobaric distribution map is called the sea level isobaric distribution map

For a project, it takes 6 hours for Party A to do it alone and 10 hours for Party B to do it alone Work alternately, 1 hour at a time, then need () hours to complete
A. 7B. 712C. 713D. 714

Party A and Party B need to complete the cooperation: 1 △ (16 + 110), = 1 △ 415, = 3.75 (hours); each person works for 3 hours, and there are 1 - (16 + 110) × 3, = 1-45, = 15; Party A works for another hour, and the rest is completed by Party B: (15-16) △ 110, = 130 △ 110, = 13 (hours); a total of 3 × 2 + 1 + 13 = 713 (hours); answer: it takes 713 hours to complete

What is the basis of judging altitude by using Asian topographic map

Remember that the middle is high and the surrounding is low. The middle is the Qinghai Tibet Plateau and the Pamirs plateau. There are many plains around, such as the North China Plain, the middle and lower reaches of the Yangtze River Plain, and the West Siberian plain. With this foundation, we can further judge according to the density of the contour lines, and the difference in altitude between each two contour lines is equal

Children have summer vacation. Where do you have summer exercises that you want them to do,

If it's a Mathematical Olympiad problem, try one example and three exercises in "infer from one instance". The amount of exercises is not large. It's suitable for cultivating interest. I used it in Grade 6, which is very good. It should be in grade 3
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