An elementary school math problem. The train crosses the bridge.

The time taken to cross the 700-meter bridge is 14 seconds.

The speed is 700 14 = 50 m s.

The train 49 seconds includes the time spent on the bridge and the length of the train itself.

Bridge and train length: 50*49=2450

Train length: 2450-700=1750

49-14=35 (seconds).

Speed: 700 divided by 35 = 200 meters per second.

Train length: 200 times 14 = 2800 km.

Let the length of the train be a, then the speed of the train is:

700+a)/49=(700-a)/14

Solution: a=3500 9 meters.

The speed of the train is: 200 9 (m s).

The speed of the train is 700 [(49-14) 2+14] m s).

The length of the train is meters).

There seems to be something wrong with the data.

Let the length of the train be x meters, the speed of the train be y, and the train will take 49 seconds from the beginning of the bridge to the complete crossing of the bridge.

700+x)/49=y

The time for the entire train to be completely on the bridge is 14 seconds, which can be obtained.

700-x)/14=y

Combine the two equations.

Solution x = m.

y=m-seconds.

Suppose that two trains go at the same time, and the distance traveled by Nogen is the same. When the fast train finishes, the slow train is still on the bridge. At this point, it takes 6 minutes.

The fast train travels 6 100 = 600 meters more than the slow train. The slow train will take another 10 minutes - 6 points = 4 points to complete. In other words, the slow train covers 600 meters in 4 minutes.

So the speed of the slow train is 600 meters 4 minutes = 150 meters minutes. The whole journey is 150 10 = 1500 meters, the length of the train is 400 meters, and the length of the cracked bridge is 1100 meters.

The train is 400 meters long 10 minutes at the usual speed 6 minutes after speeding up 4 minutes less than usual 100 meters faster than usual minutes that is to say, the usual 4 minutes is equal to 6 minutes now 6 minutes more distance 6 minutes more than 6 minutes = 600 meters The usual speed is 600 4 = 150 meters minutes According to the usual calculation, the bridge length plus the fire field length should be 150 meters minutes * 10 points = 1500 meters So the bridge length is 1500-400 = 1100 meters.

Suppose that 2 trains go at the same time, then the distance traveled is the same. When the fast train finishes, the slow train is still on the bridge. At this point, it takes 6 minutes.

The fast train travels 6 100 = 600 meters more than the slow train. The slow train will take another 10 minutes - 6 points = 4 points to complete. In other words, the slow train covers 600 meters in 4 minutes.

So the speed of the slow train is 600 meters 4 minutes = 150 meters minutes. The whole journey is 150 10 = 1500 meters, excluding the train length of 400 meters, and the bridge length is 1100 meters.

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If the train travels 100m more than 6 minutes per minute, then it travels 100*6=600m in 4 minutes, then the original speed is 600 4=150m minutes, then the distance of 10 minutes is 150*10=1500m, and the length of the bridge is 1500-400=1100m

Let the bridge length be x meters, the speed of the train is v, and the system of equations x 400 10v, x 400 6 (v 100) is listed

It is set up to be x kilometers long.

x ten 400) v one (x ten 400) (v ten 100) = 6

Let x(x ten 400) 10 = (x ten 400) 6 a 100 get x = 1100

The length of the car seen by the slow car is 150 meters, and the time is 6 seconds, so the relative speed of the two cars is 25 meters and seconds.

The length of the car seen by the express train is 200 meters, so the time is 200 25 = 8 seconds.

It's the same 6 seconds, because the two cars are traveling in the opposite direction, the speed is equal, and the length of the two cars is added together. So the time from one point to another is also equal.

You set the commander s and the speed v

A system of column equations. 1140+s=50v

1980+s=80v

Then it's good to figure it out.

Let the length of the train be x meters.

then the equation can be listed.

500+x) 30=(500-x) 20 gives x=100

The train is 100 meters.

Compare the difference between the two distances: 120-80 40 meters.

Walk an extra 40 meters and take an extra 21-17 4 seconds.

Train speed: 40-4-10 m sec.

Car length: 10*21-120 90 meters.

Or 10*17-80 90 meters.

There is a Mathematics Olympiad in the fourth grade of elementary school.

Solution: Let the speed of the train be x meters per minute.

10x=6(x+100)

10x=6x+600

4x=600

x=150, the train speed is 150 meters per minute.

150*10-400=1100 meters.

This tunnel is in deficit and has a long attack on the air bucket for 1,100 meters.