Aptitude - Problems on Trains - Discussion

Pole is given to just calculate the speed of the train, In the question, nowhere mention pole is on the platform so the answer is 65 m/s.

Since the train has to cross the platform, it is not on the platform. It has to completely cross the platform means it crosses it's length.

Therefore total distance becomes train's length+ platform's length =890m.

Time = 890/10 = 89sec.

89 sec is the correct answer.

Here pole consider as a point of reference, but platform not a point if consider engine only cross the platform from starting of platform to end (i.e also consider as crossed) 65 sec is correct, but if consider entire train (engine to the last van) cross the platform end to end length of the platform should be added hence 89sec is correct.

Why we are adding the time of poles with the time of platforms?

Length of train(distance)=240m
Time=24sec
Formula: length(distance)=speed x time
240=speed x 24
speed=240/24
speed=10sec.

Now it has to pass platform of 650m
The total length of platform =650m
train length = 240m
The total distance the train pass the platform = 650+240=890m.
Because as the train entered the platform(650m) the train remaining part was outside the platform (240m).
So total distance the train cover is 890.

Why did you add 240?

Distance= speed * time,
240/ 24=time,
Time = 10s,
Distance= speed* time.
240+ 650 combing distance = 890,
890/10= time,
89 m/s.

Here, the question is asking for a specific time taken by the train to pass the platform (650/10 =65) not the total time is taken. If at all they asked for total time, we would add them up (65+24).

240/24=10,
.:650/10=65+24=89.