Aptitude - Problems on Trains - Discussion

The speed of the train be x km/hr. Then, relative speed = (x - 5) km/hr.

Please explain it, friends.

How get 18/5?

Why they have done 125/10?

125/10 is for speed divide by time taken,
And 18/5 is to convert meter to kilometre
So that 125/10 is 25/2.

Multiply 25/2 by 18/5 to get in kilometre so it gets 45km/hr.
And the man running speed is 5km/hrs.
So, 45 + 5 is 50km/hrs.

Good explanation. Thanks all.

First we write Data:

We Have D=125m t=10s,
S=D/t =125/10=25/2 m/s.

We want to convert from m/s to km/kr.
so we multiply 25/2 into 18/5,
@When we convert km/hr to m/s we multiply by 5/18,

@When we have to convert m/s to km/hr we multiply by 18/5,

Our answer are given in km/hr so we convert according_to by multiplying 18/5.

=25/2*18/5=45 Km/hr,

let we assume train speed be X.
And Man 5 km/hr.

If given in opposite direct then we add,

Here have in the same direction so we subtract,

x-5=45 So Answer is 50.

No, it's wrong!

At last, speed came 45km. Now since it's in the same direction hence we will subtract, right.

So S=S (train (since its bigger value) - the speed given (5) ) ==>45-5 = 40.


Speed cannot be negative hence we always subtract smaller speed value FROM bigger speed value in the case for the same direction!

The train and the man are moving in the same direction we have to use subtraction.

Here, we have to find the value of X. So for that, we have to keep X separate either left side or right.

Shift 45 to left and x to right. Because we are shifting, the sign will be change (positive to negative & negative to positive).
x-5 = 45
-5 - 45 = -x
-50 = -x ....(- - = + , so - - canceled)
x = 50.

What is the difference between the relative speed of train and the speed of the train? Anyone, please explain.

I can't understand this sum please anyone explain me briefly.