Hi Karthick,

Sure, if I say that a person is moving with a constant speed of 70 kmph from A to B, that's what I'm referring to when I say that he might have minor fluctuations, he might be moving for 68 kmph for a second and 72 kmph for another second and it averages out as (68+72)/2=70, this is what is said in the question, that the person is moving with a 'constant' speed.

Average speed itself is a different thing, which means total distance traveled divided by total time taken, that is not what we are talking about here.

Hope this helps, feel free to ask if you have any doubts

Hi Karthik,

Average word here is not used in the technical sense but in the sense the over small periods the minor fluctuations can be ignored and averaged out as a constant speed.


Hope this helps, feel free to ask if you have any doubts 

please ,can you explain this with example.

Hi Garimela,

You have used the concept of relative velocity and your approach is correct.
We, on the other hand, have made equations and solved it.
Hope this helps.

Hi Syed,
The value $$\dfrac{18.5}{120}$$ is the time the trains meet from when they are 18.5 km apart. We need to calculate the distance of the meeting point from station A. So, if we add the distance travelled by train X during the time $$\dfrac{18.5}{120}$$ to 101.5, we get the distance from station A and the distance travelled by train X during this time is given as $$\dfrac{18.5}{120}\ \times\ 70$$ which is the calculation done in the solution.
Hope this helps!