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A and C start from a and B in the same direction at the same time. 24 minutes after a passes B, a catches up with B. at this time, C just walks to B, and B returns immediately. A and C keep the same direction and continue to walk. When B and C meet, a returns immediately. B and C keep the same direction and continue to walk. After another 36 minutes, a and C meet at 3 kilometers away from B, then B has already walked to a__ Km away
For the convenience of description, let a on the left and B on the right
1) According to the condition "a overtakes B 24 minutes after passing B, and C just goes to B", it means that a's speed is just equal to the sum of B's and C's speed
2) During the period when Party B returns to meet Party C, the distance between Party B and Party C is equal to that of Party A for 24 minutes, which means that Party A continues to walk to the right for 24 minutes, that is to say, the place where Party A returns is 48 minutes to the right from Party B. at the same time, according to the later conditions, the place where Party A returns is 3km to the right of Party B plus 36 minutes, so that Party A can walk 3km every 12 minutes
3) According to the time comparison between C and a, a arrives at point a 24 minutes earlier than B, and a arrives at the place where the last two people meet 72 minutes earlier than B. according to the proportional relationship, C's final distance is three times that of AB, which indicates that the distance between AB is 1500 meters
4) According to the calculation of C's time, C walked 4500 meters, while B turned around when C reached 1500, which is the first 1 / 3
So first walk 6000 meters to the right from B (according to the calculation of a 24 minutes), then walk 12000 meters to the right, according to the distance of AB 1500 meters, then B should walk 4500 meters to the left of A
The final answer is 4.5km
Xiaoming and Xiaohua ride bicycles from a and B at the same time. After 25 minutes of meeting, they continue to move forward at the same speed. After arriving at each other's starting place, they return immediately. It took Xiaohua 20 minutes from arriving at a to meeting Xiaoming for the second time. How many minutes does it take Xiaohua to ride from B to a?
In 25 minutes, the sum of the distance between two people is the distance between ab
Two encounters, the sum of the distance between two people is three times the distance between AB, the total time should be
25 * 3 = 75 minutes. It took 20 minutes from a to the second meeting, so the time between ab
75-20 = 55 minutes
A and B start from a and B at the same time. They meet for the first time at a distance of 50 km from A. after meeting, they continue to advance to their destination and return immediately. The second meeting is at 26 km from B. how many kilometers are there between a and B?
50×3-26=124
1. A and B start to climb from the foot of the mountain at the same time, and immediately go down the mountain when they reach the top of the mountain. Their speed of going down the mountain is twice as fast as their speed of going up the mountain. When a arrives at the top of the mountain, B is 400 meters away from the top of the mountain. When a returns to the bottom of the mountain, B just goes down to the middle of the mountain. Find the distance between the foot of the mountain and the top of the mountain
2. Someone walks along the sidewalk beside the tramway at the speed of 4.5 km / h. every 7.2 minutes, there is a tram passing by, and every 12 minutes, there is a tram chasing behind. If the tram starts at the same time interval and runs back and forth at the same speed, what is the speed of the tram? What is the time interval of the tram?
I'm rather stupid. I didn't understand the answers before I asked online. So please write the answers in detail. Thank you first
1. It is known that:
2V a up = v a down, 2V b up = v b down
Let the mountain height be 1, then 1 / V A + 1 / V A = 1 / V B + 1 / 2 / V B
Sorting out the above two formulas, we can get V A: v b = 6:5
(mountain height / V A above) * V B above + 400 = mountain height
Then the mountain height is 2400 meters
The second question will be answered later
What is the altitude of all places on the topographic map of our country calculated based on
In the past, China used the mean sea surface of the Yellow Sea as the elevation datum, that is, the mean sea surface obtained by Qingdao tide gauge from 1950 to 1956 as the elevation datum, which is called the 56 year Yellow Sea elevation system. The measured elevation of the national leveling origin (Qingdao origin) is 72.289 meters
The 1985 National elevation datum is determined by using the tidal data of Qingdao tide station from 1952 to 1979. The measured elevation of the national leveling origin (Qingdao origin) is 72.260 M. that is, the 1985 elevation datum is 0.029 m higher than the original 1956 average sea level of the Yellow Sea
There is a balance, the weight of things that can be weighed is between 1-30g. Now there are only 5 special weights of 1g, 2G, 4G, 8g and 16g. How can we use these 5 weights to weigh objects weighing 27g?
The total weight of five weights is 31 grams. Now we need to weigh 27 grams of objects, and take 4 grams of weights from them
What's the elevation on the topographic map of India
Altitude refers to the vertical distance of a place above sea level
A man walked along the road and a car came to him. He asked the driver, "is there a cyclist behind?" The driver replied, "I passed a cyclist 10 minutes ago." the cyclist walked on for 10 minutes and met the cyclist. If the speed of the bicycle is three times that of the pedestrian, how many times is the speed of the car?
Suppose the pedestrian speed is x, then the car speed is 3x + 3x + x = 7x, thus the car speed is 7 times of the pedestrian speed. Answer: the car speed is 7 times of the pedestrian speed
What is the contour line? What is the elevation of each point on the same contour line
..
Contour, equal altitude,
5. Someone walks along the sidewalk beside the tramway at the speed of 4.5 km / h. every 7.2 minutes, there is a tram passing by, and every 12 minutes, there is a tram chasing behind. If the tram starts at the same time interval and runs back and forth at the same speed, what is the speed of the tram? What is the time interval of the tram starting?
6. There is a small road beside the railway. A 110 meter long train goes southward at the speed of 30 km / h. at 8 o'clock, it catches up with a worker walking southward and leaves him 15 seconds later. At 8:6, it meets a farmer walking northward and leaves the farmer 12 seconds later. Q: when did the worker and the farmer meet?
7. Xiaohong takes the train from her home to the railway station. She travels 4 kilometers per hour. When the train leaves, she is still 1 kilometer away from the station. If she travels 5 kilometers per hour, she will arrive at the station 12 minutes earlier. How many kilometers is Xiaohong's home from the railway station?
The faster, the better. It's better to have a graph or use an equation to solve it,
1：
If the tram speed is V, the first step is to turn minutes into hours: 7.2 minutes = 0.12 hours, 12 minutes = 0.2 hours
Then driving face-to-face is actually a meeting problem. We can first set the distance taken by the tram within a time interval as S
Then: (V + 4.5) 0.12 = s
Driving from the back is the pursuit problem,
Then: (v-4.5) 0.2 = s
It can be solved that v = 18km / h, and the time interval can also be calculated as 9 minutes
2：
In fact, it is to find their speed and the distance between them
Let's find the speed first
The worker's number is set to X
（30-X）*15/3600=110/1000
The result is x = 3.6km/h
Let's set the farmer's speed to y
（30+Y）*12/3600=110/1000
Y = 3km / h
Then, at 8 o'clock, the train happened to be at a starting point. Six minutes later, the workers met the farmers. This is because the train has been running for six minutes, and the workers have also walked for six minutes. How much distance is left
30 * 6 / 60-3.6 / 6 / 60 = 2.64 km
64 / (3.6 + 3) = 0.4 hours, that is 24 minutes
So when we meet, it's 8:6 plus 24 minutes, that's 8:30
3：
Directly set the distance to X
1 / 4 = 0.25 hours 12 / 60 = 0.2 hours
Then: X / 4-0.25 = x / 5 + 0.2
X = 9 km
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