Aptitude - Problems on Trains - Discussion

If we consider relative speed = 46-36 = 10 (km/h), then at this speed the faster train needs to cover just the length of the slowest train (so we have just x not 2*x). Length of one train equals 100 m.

Also d1 = 460 m faster train in 36 s.

d2 = 360 m slower train in 36 s.

----x, d1.

---x, d2.

Let's suppose the length of train is x = 50 m, then d1-x = 460-50 = 410 m! = 360 m (distance covered by the slowest train).

So x = 100 m, length of one train.

If faster train passes the slower train in 36 seconds then slower train passes the faster train in how many seconds?

Length of the train = X.

Equal length of 2 trains = 2X.

If same direction = u-v = (46-36)km/hr = 10km/hr.

Speed = (Distance or length)/Time.

10 km/hr = 2X/36 sec.

(10*5/18) m/sec = 2X/36 sec.

X = 50 sec answer.

(Note : if opposite direction = u+v).

Let the length of each train is X.

Than total length which should be covered to pass the train = 2X.

The speed of train to pass the 2X distance = 2X/36.

The relative distance of trains = 46-36 = 10 km /hr.

So 10*(5/18) = 2X/36.

X = 50 answer.

In this problem length of two train will be equal therefore L = 2X.
That is distance covered = 2X.

D = SPEED*TIME.
2X = 10*(5/18)*36.

Solve the above equation you can easily get a answer.

Trains are running in same direction so the relative speed is different.

Speed of train 1 - speed of train 2.
46 - 39 = 10 Km/hr.

Convert Km/hr to m/sec.
10* 5/18 = 5/3.

Now multiply with faster train cross time ie 36 with obtained value.
36*5/3 = 50m.

Since we are talking about relative speed (means b/w two trains. ).

Hence taking distance also combing length of two trains.

At final we are making two train details as single train details after finding we can extract two trains details.

2x/36 = 25/9.

Please make it cross multiplication simply,
(2x*9) = 25*36),

=>18x = 900.
=>x = 900/18.
=>x = 50m.

Can any one explain how the step below ?

2x /36 = 25 /9.

By using the formula, if we solve the problem in SI unit we get 49.86 as answer.