Aptitude - Problems on Trains - Discussion

Why it is divided 125/10? Please explain.

Relative speed subtracted by actual speed so we get X - 5.

How x-5 came?

Wrong solution.

Man also traveled a distance of 5*5/18*10=125/9 m in 10 sec. So this distance should be added to 125 m when calculating relative speed, so relative speed = (125+125/9)/10 = 125/9 m/s = 125/9 * 18/5 km/s = 50 km/hr.

So the speed of the train is 50+5 = 55 km/hr.

x-5 = 45.
x = 45+5(because when 5 goes from the left side to right then it will be added into 45).

So,
x = 50 Answer.

It's 50 m/s unit.

We 1st Find the speed of train relative to man Vr.
Man and train moved in the same direction = (V-U).
V = Speed of the train.
U = Speed of man.
Vr = (V-U).

If only one of the speed is given then how will we consider that which one is to be subtracted or not?

Why 5 - X not taken?

According to the question,

Trains length = 125m (distance).
Speed = 10sec,
Mans speed = 5km/hr.

The km the train hasn't travelled is not been given so take it as = X km/hr.
Man moves in the same direction = 5km/hr .

When two bodies are moving in the same direction then you will have to subtract it. If the person is moving on the opposite side he feels the train is moving faster hence u got to add But here it's on the same direction.

So, it's (x-5)km/hr.
When you want to convert kilometre into metres multiply with 5/18
So , (x-5) 5/18 ---> (1) i.e time

Time =distance/speed.
= 125/10 --> (2).

Therefore,
Time = distance/speed.
(X-5) 5/18 = 125/10,
(X-5)5/18 = 25/2,
(X-5) = 25/2 * 18/5 (simple cancellation).
(X-5) = 45,
X= 45+ 5,
X= 50.