Aptitude - Problems on Trains - Discussion

Actually, whenever a train crosses platform we are considering the length of train+length of the platform, similarly, in this case, we consider the length of tunnel+length of train i.e7/2+1/4.

Why in this sum we didn't change speed kmph into m/sec?

Guys 1mile = 1.6km.
For train speed:
So 75mph = 75*1.6 = 120kmph.

For tunnel length and train length:
7/2miles*1.6=5.6km and 1/4miles*1.6=0.4km.
So total distance=5.6+0.4=6km.

Now to calculate the time we have the formulae is t=d/s.
Lets convert all data into metres.
So 6km*1000=6000m.

Speed=120*5/18 m/sec=100/3 m/sec.
So t=6000/100/3 which is equal to 18000/100=180seconds.

So to convert seconds into minutes is(1min=60sec) 180/60=3min.
Try to understand because it's too long.

mph means mile per hour or metres per hour?

Which one is correct?

Hey guys, don't much obsessed with it. It's quite simple as it is.

1 mile=1.609 km.

Distance travelled by train = (7/2+1/4) only.

For easy understanding.

Assume that you are standing at the tunnel starting end with a stopwatch and now the train is coming and (note that in the question he said that from the front end entres) that means when the engine comes to the position where you are standing then you start the stopwatch from that point, the train goes on goes on and after some time the engine part reaches to the exit end of the tunnel and (note that in the question he said time should be calculated till the rear emerges) so don't stop the stopwatch let the train go and the strain is going going going and after some time the last bhogi (last part) of the train left the tunnel then you need to stop the stopwatch.

Then note the time. So that time is only required.

Observe carefully in this entire process the train is travelling only the tunnel length and its own length.

And coming to question.

The question is error instead of metres he has given miles.

So don't bother much about this.

If you guys have any doubt about the above explanation just take a pen and paper and draw a line and observe the above explanation. Then You guys get that.

I hope you understand.

Have a nice day.

15/4.

(7/2 +1/4) = let take hcm of this i.e. 4.
Then, (7*2/4 +1/4),
(14+1/4)=15/4.

Yeah, We have to convert the mile to km.

How it's comes 15/4?

Please explain.

Because 75mph that means 75 miles per hour, not metres.

@All.

Assume that there's a platform of length 7/2 miles and train of length 1/4 miles.
So now we just have to calculate the time taken by train to pass the platform.
Hence total distance = 15/4 miles.

No need to add 1/4 twice.

Hope you will understand.