Aptitude - Problems on Trains - Discussion

The length of the platform = (speed of train * time taken to pass the platform)/(1 - (time taken to pass the man/time taken to pass the platform))

In this case:
The length of platform = (54 * 36)/(1 - (20 / 36))
= (54*36)/(1-(20/36))
= (1944)/(1-(5/9))
= 1944/(4/9)
= 1944 * (9/4) = 240 meters.

D = S x T.
D = (54x 5*18) x (36-20).
D = 15 x 16.
D = 240m/s.

Since the options given are in meters, we must first convert given into m/s.

Speed of train =54km/hr = 54*5/18 = 15m/s.
Then find the length of the train using D = S * T eqn in the case of a man

Length of train =15 m/s *20 secs =300m.
Then while passing the platform, Total length =(train length +platform length) = 15m/s * 36 secs =540m.
Therefore platform length = 540m - 300m = 240m.

Speed=54*5/18=15m/s.
Distance = 36 - 20s = 16,
=>15*16=240m.

Speed = 54km/hr
54*5/18 = 15m/s.

Time = 36-20 =16sec.

Length of the platform(D)=?
Distance = speed * time.
Distance = 15 * 16.
Distance = 240 m.

Given the speed of the train is 54 km/hr.

In 60*60second.
15m in 1 seconds.
90m in 6 seconds.
150m in 10 seconds.
240m in 16 seconds.

Because the time diff is 16 seconds Platform length.

36sec it passes both man and platform but they ask only for platform so we have to deduct man standing passes 20sec.
36-20 = 16sec it passes only for the platform.
Then find out using this formula;
Distance = speed * time.
We know speed = 54km/hr.
Time = 16sec.
D = 54*5/18 m/sec.
D = 240m.

t1 =36s
t2 = 20s
s= 54km/hr
l=??

d1 = s*t
d1 = 54*(5/18) * 36
d1 = 15m/s * 36
d1 = 540m.

d2 = 15*20.
d2 = 300m.3

300m is the distance up to the man standing and the length of the total platform would be greater than this. so,

300 + x = 540m.
x = 240m.

Let's take the train length for the man and station platform the same, then
D = D.
S * t = s * t.
15 * 36 = 15 * 20,
540 = 300.
540 - 300.
240.
Speed conversion 54 * 5/18 = 15.

@All.

Here is the explanation:

Train speed is 54 km/h
(Sum of the seconds taken for cross=36-20 =16 sec.

If we know how many meters crossed in 1 sec we can find how long that travelled in 16 sec)
The train can cross 54 km per 1 hour.
54km =5400m (because we need ans in m)
1 hour = 60mnts and 60 sec total 3600 sec
Check the unit mentioned km/h.
We have 54000 for km and 3600 for hour.
Substitute this in km/h.
54000/3600 = 540/36 = 180/12.

= 90/6 = 15.
So the train can cross 15m per sec
So it takes 1 sec for 15m.
Then it takes 16 sec to cross.
15 * 16 = 240 m
So, the train crossed 240 m length of the platform.