The length of the express train is 70 meters and the length of the local train is 80 meters. If two trains go in the same direction, the time it takes for the express train to catch up with the local train and leave the local train completely A fast train is 70 meters long and a slow train is 80 meters long. If two trains are running in the same direction, it takes 20 seconds for the fast train to catch up with the slow train and completely leave the slow train. If two trains are running in the opposite direction, the time from meeting to leaving is 4 seconds. How many kilometers per hour can the two trains travel? It must be solved by equation

The length of the express train is 70 meters and the length of the local train is 80 meters. If two trains go in the same direction, the time it takes for the express train to catch up with the local train and leave the local train completely A fast train is 70 meters long and a slow train is 80 meters long. If two trains are running in the same direction, it takes 20 seconds for the fast train to catch up with the slow train and completely leave the slow train. If two trains are running in the opposite direction, the time from meeting to leaving is 4 seconds. How many kilometers per hour can the two trains travel? It must be solved by equation

Master of red apple paradise,
Let the speed of the fast train be meters per second, and that of the slow train be y meters per second
20（x-y）=70+80,20x-20y=150,2x-2y=15...（1）
4（x+y）=70+80,2x+2y=75...（2）
(1) + (2) get
4x=90
x=22.5
y=15
22.5 M / S = 81 km / h
15 m / S = 54 km / h

It takes 20 seconds for the express train to catch up with the local train and leave the local train completely. If the two trains are running in opposite directions, the time from meeting to leaving is 4 seconds. How long does it take for the two trains to walk thousands of meters per hour?

Speed sum = (70 + 80) × 4 = 75 / 2m / s speed and = (70 + 80) × 20 = 15 / 2m / s express speed = (75 / 2 + 15 / 2) × 2 = 45 / 2m / S = 25 / 4km / h express speed = (75 / 2-15 / 2) × 2 = 15m / S = 25 / 6km / h your praise is my driving force

A fast train and a slow train run in opposite directions. The body length of the fast train is 270 meters, and the body length of the slow train is 360 meters. The time for people sitting on the fast train to see the slow train passing is 12 seconds. How long does it take for people sitting on the slow train to see the fast train passing? (ask for answers and ideas)

The relative speed of the two cars is the same, which is v fast + V slow. The difference is that the length of each other's cars is different. Therefore, the length of the slow car is 360 meters for the fast car to see the slow car, and 270 meters for the slow car to see the fast car
The results show that t slow / T fast = 270 / 360, t slow = 12 * 270 / 360 = 9 seconds

An express train is 70 meters long and a local train is 80 meters long. If the two trains are going in the same direction, it takes one minute for the express train to catch up with the local train and leave the local train. If the two trains are going in the opposite direction, it only takes 12 seconds for the express train and the local train to meet and leave the local train?

Let the speed of fast train and slow train be x and Y respectively
（70+80）÷（x+y）=12
（70+80）÷（x-y）=1×60
X = 7.5 M / s, y = 5 m / S