A train 1km long goes through a 1km tunnel. If the train is traveling 15kph, how many mins to pass through?

Question

What method should I use to solve this problem?

Answer 1

Right...you wanna know how long the train takes to run 2 Km...which is 8 minutes...15Km = 15.000 m

15.000 : 60 = 250 m in 1 min, so 2000 m in 8 mins.

Answer 2

Use common sense.  Draw 2 lines, one for each end of the tunnel.  Then draw 2 more lines, one for the front of the train and one for the back.  You have to count all the time that any part of the train will be in the tunnel.  Imagine there is 1 person in the front of the train and another person at the back of the tunnel.  At 15 km per hour, it would take one person 4 min to get from one end of the tunnel to the other, but just when they get to the other end, the person at the back of the train is just entering the tunnel.  So it will take ANOTHER 4 minutes for them to get through.  So the answer is 8 minutes.

Answer 3

When the front of the train reaches the tunnel the back of the train is 1km away from the tunnel and 2km from the end of the tunnel. How long does it take the train to travel 2km?

Answer 4

let x be the time the front of the train enters the tunnel

let y be the time the back of the train exits the tunnel

x must travel 1 km at 15kph taking .0666 hours

y gets to the start of the tunnel at .0666 time elapsed and takes .0666 hours to pass the tunnel so

.0666+.0666 =.1332 hours or 7.99 minutes

Check 15kph means .25 km/min so if the train has to travel 2 km it will take 8 minutes (2/.25)

Answer 5

The train has to travel 2 km

15 km/hr * t = 2km

t = 2/15 hr

t = 8 min

Answer 6

= 60(2[1 kilometer/15 kph]) minutes

= 60(2/15) minutes

= (60/15)(2/[15/15]) minutes

= 4(2) minutes

= 8 minutes

Answer: 8 minutes

Proof (train has to move 2 km—it's head through the tunnel is 1 km and the tail through the tunnel is another kilometer):

= (8 min * 15 kph) km

= (8/60 hr * 15 kph) km

= (2/15 hr * 15 kph) km

= 30/15 km

= 2 km