Aptitude - Problems on Trains - Discussion

Normally we need length of the train gven data has speed and length of the platform and clue is 15 sec because the train has passed the signal post in 15 sec so we have the differnce as 25-15 we get 10 sec.

When we use 25sec as base as nareen and anil said
we should use options which option will verify us anns =10 sec
we can use 25 sec also but with the help of options we can come out .or else we should follow 15 sec as the speed of the train ok.

Hope u got it.

(distance or length)/speed=time
in the question both length and speed of train is not given.
So length is x and speed is y.
time given is 15sec.
so x/y=15

and in the next equation we can not write x/y so we interchange it before as y=x/15.
actually it means one and same but to use in equation in right way we have to do it in this way :)

Please explain the question in detail.

Thank you pavan.

Please let me know if we can take time as 25-15=10sec.
And solve it as,
Speed=100/10=10sec.

So D/T=S
It means x+100/25=10
x+100=10*25
x=250-100
x=150m.

Let train's length be x meters,

Then, train speed=train length/the time taken to cross the poll.

= x/15.

Train speed=total distance/the time to cross the platform,

x/15 = (x+100)/25.

x = 150.

Let Speed = x m/s.
Distance = 15x m = 15*10 = 150.

Time = 15 secs.
Using d = st,

15x + 100) = 25x.
x = 10.

Therefore - distance = 15x m = 15*10 = 150.

Let trains length is X meter.

When cross the pole the train goes in 1 sec = (100 + X) /25.
When cross the platform the train goes in 1 sec = X/25.

The equation:

(100 + X) /25 = X/25.
X=150.

So the length is 150 m.

T = 15 Sec.
T+100 = 25 Sec.
--------------
T = 100/10 = 10 m/s where 10 sec. = 25-10(difference).
T = Length of the train
T = 15 Sec.*10 m/s=150 m.

Length of the train = 150 m.

Speed*Time = Distance.

S*T = D.

T = 25-15 = 10.

S = D/t = x/15, x = length of train.

(x/15)*10 = 100.

x = 150m.