Aptitude - Problems on Trains - Discussion

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.

240=24sec.
then 650=x.
240x=650*24,
240x/240=650*24/240,
= 65m/s.

It should be 65 sec only.

Analysis: The speed of the train is the same in both cases. For the constant speed,

(distance/time) in first case = (distance/time) in second case.

240/24=650/x==> x = 65 sec.

Here, it should come 890 instead of 650. We should add both the values. So the correct answer is 89sec.

The Answer is 65s, because the question in not mention both pole and platform then why we calculate both?

Accurate Answer is 89 sec only.

@All.

In case of crossing a man/post/pole:

Usually, we will ignore the length of man/post/pole. If you want the result of speed in 'millimetres/second' accuracy, you can add length of the man or pole to the length of the train.

I think the answer is 65sec.
240m long a pole passes away in 24 sec.
So, Time = distance ÷ speed.

240÷24 = 10 sec.

How long will take to pass a platform 650 m long?

Ans-650÷10 = 65m/s.

As the train has to pass the platform its length need to be considered so they added 240 to the platform length.

As the train crosses the platform, we have to add the length of the train to the platform length. (remember this the train engine is at the platform starting point).

By using the pole concept in the given problem we can find the speed of the train.

Speed=distance*time.

240/24=10sec.

Because, the train to cross the platform, the total length travelled to cross the platform is equal to the length of the train plus length of the platform,

Speed= (240+650) /10.
= 890/10.
= 89.