The light dimmed, and the train pulled into the Black Rock Mountain Passage, and there was a sobbing

It is thought-provoking and intriguing, in fact, there is also a structural role at the end of every narrative to summarize the whole text, but if it is just this sentence, there should be none. See if you take care of the previous text and the title.

From the beginning of the tunnel to the full exit, the train travels in 30 seconds: tunnel length + train length.

The length of the whole train in the tunnel is: tunnel length - train length 20 seconds, and the train speed is v train length l

30V=500+L 20V=500-L: L=100m.

The train is 100 meters long.

The solution of the unary equation is as follows: The train enters the tunnel from the beginning to the time it completely exits, and the distance it takes is 30 seconds for the tunnel length + train length.

The length of the entire train in the tunnel is: tunnel length - train length 20 seconds rounding the train length x meters.

Train speed = (500+x) 30=(500-x) 20 solution x=100 So the train is 100 meters long.

Set up the train length A, the train speed is V.

500+a) is the distance traveled by the train from the beginning to the time it fully exits.

500+a) v = 30 seconds.

When the train is in the tunnel, it is the distance from the end of the train entering the tunnel to the time when the head of the train crosses the tunnel.

So (500-a) v=20s

v=20m/s

A return train enters a 500-meter-long tunnel, it takes 30 seconds from entering to completely leaving, and the train is completely in the tunnel in 20 seconds, find the speed and length of the train?

The length of the train is l meters.

30*(500 2L) 20 = 500+L: L=m.

The train is long in meters.

30 seconds to walk a tunnel + train length, 20 seconds to walk a tunnel - train length, the speed is the same, expressed by an equation is: (500 + x) 30 = (500 - x) 20, the solution is x = 100, that is to say, the train is 100 meters long.

Solution: Let the length of the train be x meters.

Analysis: From the beginning of entry to full exit, the distance is 500+x, the train is completely inside the tunnel, and the distance is: 500-x

Equiquantity relation: The speed of the train does not change.

500+x)/30=(500-x)/203(500-x)=2(500+x)

1500-3x=1000+2x

5x=500

x=100A:.

Is there a problem with your question, the train is 15 kilometers per second, this is too scary. It should be 15m s!

Completely through the tunnel, that is, the length of the train body plus the length of the tunnel. Then use (600+150) 15=50 seconds.

If you use 15 kilometers per second, you have to convert it, 15 kilometers per second = 15000m s (600 + 150) 15000 = seconds.

The distance that the train passes through is the length of the tunnel plus the length of the train body, a total of 600 + 150 = 750 meters, and the distance speed = time, so it is 750 15000 =

(600+150) divided by 15

15 kilometers per second should be 15 meters.

Solution: Let the train captain be x.

Because: it takes 10 minutes for a train to enter the tunnel from the front of the train to the back of the tunnel to exit the tunnel: the distance of the train is 4800m+2x

According to t=s v, we get :

10min=(4800m+2x) / (500m/min)5000m=4800m+2x

2x=200m

x=100m

A: The length of this train is 100 meters.

If you already know that the light hits t seconds, then you only need to know the speed of the train, and you can know that it took 30 seconds to drive into the tunnel until it left.

The total distance traveled by the train is the length of the tunnel plus the length of the train itself, so if the train speed is V, then there is.

v*t+600）/v=30

Solve the equation to get the answer c

If you want to find the length of the tunnel:

Solution: The tunnel is x meters long.

The columnable equations are as follows.

x÷32=（x+180）÷45

Solution x = 480 meters.

If you want the speed: Solution: Set the speed of the banquet to be x meters.

The columnable equations are as follows.

45x-32x=180

Solve blindness x = 15 m sec.

Tunnel length: Solution: Set the tunnel length to clear the ant x meters.

The columnable equations are as follows.

x 32=(x + 180) 45

Solution x = 480 meters.

Car speed: Solution: Set the speed of the car to x meters and seconds.

The columnable equations are as follows.

45x-32x=180

The solution is x=15 m/s.

If you want to find the speed of the train: let the train speed be x meters and seconds, 45x-180=180+32x

It's 100 meters! In terms of speed: if the length of the train is x, the train is completely in the tunnel, that is, the rear of the train is completely entering and the front of the train is about to leave, it can be seen that it is 500-x, and the distance that the train does not completely travel in the tunnel is 2x, and the speed is (500-x) 20 = 2x (30-20), and the solution is x 100

Analysis: If the train leaves the tunnel completely, then we take the tail of the train leaving the tunnel as a reference point, then the total distance traveled by the train is +500 car length

The current train length is X

The speed is x (30-20).

then x (30-20)*20=500

x = 250 meters.

Let the train be x meters long and the speed y y

500－ x）／y＝20

500＋2x）／y＝30

x＝50／3

The distance traveled by the train through the tunnel is equivalent to the length of the train plus the length of the tunnel, so the length of the train is x meters.

It can be columnarized as:

x+4700=1200*4

x=100

If the length of the train is x meters, then there is x=(1200*4)-4700 x=100

Solution: (1) Let the speed of the train be v meters and seconds, according to the topic, 14v = 120 + 160, and the solution is v = 20

A: The train travels at a speed of 20 meters per second.

2) When 0 x 6, y=20x;

When 6 x 8, y=120;

When 8 x 14, y=120-20(x-8)=-20x+280(3) function image.

Let the length of the train in the tunnel be y when the locomotive enters the tunnel entrance for x seconds

1. Find the speed of the train.

2. When x is less than or equal to 14 and greater than or equal to 0, find the analytic formula of the function of y and x.

1. (120+160) 14=20 then the train speed is 20 meters per second.

2. The function should be a piecewise function, when x is greater than or equal to 0 and less than or equal to 6, y=20x

When x is greater than or equal to 6 and less than or equal to 8, y=120 and when x is greater than or equal to 8 and less than or equal to 14, y=120-20 (x-8), which is reduced to y=280-20x

When x is greater than 14, y=0

s full = s tunnel + s length = 120 + 160 = 280 mv = s full x = 280 14 = 20 m s when x = 0 6 s, y = v x =2 0 x when x = 6 8 s, y = s length = 120 when x = 8 12 s, y = s length — v x = 120 x