Aptitude - Problems on Trains - Discussion

Case 1: When they are in opposite direction.

Length of train in m = (Speed of train + Speed of man) in m/sec*time in sec.

Case 2: When they are in same direction.

Length of train in m = (Speed of train - Speed of man) in m/sec*time in sec.

110 m = (60 kmph + 6 kmph) * time (sec).

110 m = 66 kmph * time (sec).

110 m = 66*5/18 (m/sec) * time (sec).

Time (sec) = 110/18.333.

Time (sec) = 6 sec.

Hint: To convert km/hr = m/sec multiply by 5/18.

To convert m/sec = km/hr multiply by 18/5.

@Thili.

I agree with you.

The distance the man runs (X) towards train will be decrease the total distance, i.e 110-X mts.

Hence the time will decrease below 6 seconds.

Also since we have 2 variables distance traveled b the man towards train and the time taken for train to pass the man.

Can someone explain this solution clearly.

Hi, I am confused with the solution provided here:

Let the time taken be - X.
Relative speed = 66 KMPH = 55/3 meters/sec.
Distance = 110 + (5/3)X, (5/3)X being the distance covered by man.
Distance = Speed * Time.
(5/3)X +110 = (55/3) * X.

On resolving this, X comes to 6.6 seconds.

Please correct me when I am wrong.

In the question they did not mentioned that the whether the train is moving on platform are not. If they mentioned any pole are platform means we want to consider the distance of man moving in opposite direction. So I think we don't consider the distance.

@Melvin Michael.

It's true that if we consider the distance taken by a man in running towards the train , the answer becomes 6.6.

But the man is running in the opposite direction so sign of that distance becomes negative and hence,
Ans becomes 5.5.

Both the man and train moving in opposite to each other so while the train crosses man, man will also move some distance so total distance travel by train will be different not only its own length.

Hence the answer is 6.6 sec.

Here is solution in simple way:.
As we know speed will add in case of opp direction so,
Speed= (60+6) =66km/h.
66*5/18=55/3m/sec (for change km/h into m/sec).
Length=110m.
Distance=s*t.
110=55/3*t.
Hence.
t=330/55=6sec.

hi friend
tarun
step 1) opposite direction so we add it(60+6)
step 2) we convert km/hour into m/sec so we multiply by 5/18
step 3)speed=distance/time
spep 4) time=distance/speed

i think now u get it clearly.

@Arun

speed=distance/time

time=distance/speed

speed = 66*5/18 [Converting km/hr to m/sec]

= 55/3 m/sec.


Therefore, time = 110/55*3

= 110*3/55

= 6 sec

i think u will understand now

To pass the man train should go distance of train and the which was ran by the man.

Then why don't you care about the distance of man run. Train should go that distance also to pass the train.