Aptitude - Problems on Trains - Discussion

Please explain it, easily. I can't able to do it.

@All.

Refer Rajkumar explanation, he explained very well.

Thanks @Rajkumar.

T = (L1 + L2)/(S1 + S2),
T * (S1 - S2) = L1 + L2,
36 * 10 * 5/18 = L1 + L2,
100 = L1 + L2.
Given that L1 = L2.
Then,
2L1 = 100.
L1 = 50.

Why have you taken the relative speed here? Please explain.

Here, two trains are equal length & same direction but speed is different that's why we calculate the relative speed = u - v.

As per the given condition, the faster train crosses the slower train. So it means that.

First,
The fast train crosses the slow train of distance x metre.

Second,
Note (the fast train is not a point,). So it has a length of x meter to cross.

Finally x + x = 2X.

Hope you get it.

Length of both the trains is x+x = 2xkm/hr.
Relative speed = 46-36 = 10km/hr.
Time = 36 sec.
L= 10 * (5/18) * 36.
= 100,
2l= 100,
L= 100/2,
L= 50.

46-36 = 10,
10*5/18 = 2.77,
2.77*36s = 100,
So, the length of train is 100/2 = 50m.

The relative speed = (46-36)=10km/h.
converted into m/s = 10 * 5/18 = 25/9m/s -------------------------- 46km/h train 1 faster train
(x) 36 sec -------------------------- 36km/h train 2 slower train.
Find out the length of the train (distance) d = s * t.
25/9 * 36 = 100both train.
100/2 find the each train distance,
50.

The simple math is, 46km/1h - 36km/1h= 10km/1h. Now; it can be converted into meter/second that is 10km*1000m/3600sec. 10000m/3600s= 2.778m/1sec.


Now, for the difference of 2.778 meter/1sec the faster train cross the slower train in 36 sec. So, the distance the faster train cross 36sec * 2.778 meter= 100 meters.
This 100 meters distance/way is the length of two trains (faster&slower).
As if, two trains' length is same. So, one train's length is; 100/2= 50 meters.