Aptitude - Problems on Trains - Discussion

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Train Bridge Train(and timer
(and timer stops here)
starts here)
<------------------------>
This is distance travelled by train in 30 sec (375m)
<--------------><-------->
Lenght of bridge Lenght of train (130m)
Lenght of bridge = distance travelled in 30 sec - lenght of train
Hence proved. : )

@VINU
Exactly that would be the total distance travelled by train in 30 sec

45 km/hr = 12.5 m/s
then the train travel 375 m in 30 seconds
[i.e] 12.5[speed] * 30[total time to reach] = 375[this is the time the train completely out of the bridge]
then the length of bridge is 375 - 130[length of train]= 245

Am telling the easy way to solve this problem......
in basic formula is
L=speed*time
here we wanna 2 find length of the bridge so,

L1+L2=speed *time(L1=length of the train,L2=length of the bridge)v can get d ans easily....

Yes shahul I like your tact to solve this problem.

HI All,

Let's simplify this:

Distance traveled(d) = speed(d) * time(t) taken to travel that distance(d)

Speed is 45km/h.
Since answer needs to be in meter, let's convert Km/h into m/sec.

so, 45*(1000/3600), because 1km=1000mtr and 1hr= 3600sec(60minutes*60 sec per minute).

So, our m/sec speed(s) comes to be 45*(5/18)=25/2mtr per sec.
We have s = 25/2m/sec and t= 30 secs. so d = s*t =375mtr.

Since train itself is 130mtr long it wouldn't travel all 375mtr. So, the distance actually traveled(bridge length)by train is 375mtr- 130mtr = 245mtr.

hope this helps.

Hi coolburn its nice explanation

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

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

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