Question

A train 800 metres long is running at a speed of 78 km/hr. If it crosses a tunnel in 1 minute, then the length of the tunnel (in meters) is:​

Answer 1

Step-by-step explanation:

Let us start the solution to the above question by letting the length of the tunnel be x meters. So, the distance travelled by tunnel is given by (x+800) meters, because the length of the train is added to the distance. The length of train is added because the timer was started as soon as the engine entered the tunnel but it was stopped when the last cart of the train left the tunnel, by the time the timer was stopped the engine was 800 meters away from the end of the tunnel.

Also, we know that distance=speed × time , so the distance travelled in 1 minute, i.e., 160hrs is :

distance=78 × 160

Also, distance is equal to (x+800) meters which is equal to x+8001000 km .

x+8001000=78×160

⇒x+800=1300

⇒x=500 meters

So, the length of the tunnel is 500 meters.