Aptitude - Problems on Trains - Discussion

Your are right sushi.

Please help why we consider both lengths separately?

If the train is crossed 130m length in 10 sec it also covered length of bridge?

Why we are again consider the bridge length?

The train is already crossed the bridge in 10 sec. So the length of the bridge also covered.

HEY. I have a doubt. The length of train is already covering some length of the bridge. Then why we consider both lengths separately?

Formula is = (Length of the train + Length of the object)=(Speed of the train* Time of the object).

dis=len of train+bridge length(take a bridge as x)
130+x
speed=45km/hr=45*5/18=25/2
time=30sec
dis=speed*time
130+x=25/2*30
130+x=375
x=245m.

Thanks Nil.

Given:
1. Length of the train = 130 m
2. Speed of the train = 45 km/hr or (25/2) m/s
3. Time taken by the train to cross bridge = 30s

Find:
Length of the bridge = x meter

First, convert speed of the train from km/hr into m/s
So, speed of the train in m/s = [45*(5/18)] km/hr = (25/2) m/s

Now,
Distance(or length) = speed * time

But,Distance = (Length of the bridge + Length of the train) = speed * time
Distance = x + 130 = (25/2) * 30

x+130 = 375
x = 375 - 130
Length of the bridge = 245 m

Here, A Train 130meter long.

Speed of train=45km/hr=45000m/3600sec=12.5m/sec.

Within 30sec that train cross distance=12.5m/sec*30sec=375m/30sec.

So,Length of Bridge=Cross distance - length of Train
=375-130=245Meters.

Therefore , The Length of Train= 245Meters.

This problem is very easy to solve
speed(v) of train=45km/hr
length of train(d)=130m
time(t)=30sec
d=v*t
d=(45*5/18)*30
d=(25/2)*30
d=375
length of bridge(x)=d-length of train
x=375-130
x=245m

First of all arragne them in D= ST.
S = D/T or T = D/S.

Is 45 km/hr relative speed between the bridge and the train?