Aptitude - Problems on Trains - Discussion

Another easy method to solve this problem without using the variable x. Because if we use variable x for all the problems it will b bit confusing.

Solution is in question they asked about length so the formula is.

Distance = speed * time.

Since in question they had given speed in km/hr and the remaining terms are given in seconds added to that answer too given in meters.

Henceforth, its converted to m/sec.

So for converting it is been multiplied with 5/18.
Speed = 54 * (5/18).
= 15.

Since the train and the man in same direction it should be subtracted according to the rule.

So, time = (36-20).
= 16.

Now apply it in the formula.

Distance = speed * time.
= 15 * 16.
= 240.

Answer is 240.

We know that,
s = d*t.

The train has a speed of 54 km/hr.

i.e 54(5/18) = 15 m/sec.
Total distance is sum of train dist and platform distance.

Here we should consider one thing i.e a man is standing 20 sec in plat form during the train crosses the platform. Hence that will gives the length of train So the train length is,
15*20=300 m(s=d*t).

Total distance 300+x ;x is the dist of platform.

Total time 36 sec. So,
300+x/36 = 15.
Finally x = 240 meters.

If the person is standing at the starting point of the platform means the platform length is 240m otherwise its length cannot be calculated. Because if the person standing between any point of platform means it will addition of part of platform and length of train.

If the train cross the platform in 36 sec. Ok in the same time it also cross it's own length of 300 mt. Then we have to subtract the time taken by the train passing it's own length i.e. 20sec.

Then the platform length should be crossed in (36-20) sec =16 sec. Then why (36+20) sec?

Then what is the position of the man on the platform?

I solved in my own knowledge.

./...................

(think "....." it is a platform and a man"/" standing at the very beginning of the platform).

The train passes the station platform in 36 sec and passes the man"/" standing on the platform in 20 sec.

The length of the platform including the man is= 36*15=540 m.
And the length of the man including platform is=20*15=300 m.

So, the length of exact platform=540-300=240 m.

Yeah I have same question that why are we taking 15*20?

If the man is at starting point of platform then answer is 240.

If the man is at any where of the platform then answer is 540.

They have asked for total length of the platform and answer must be 300+240 = 540 mt. Am I right ? can anyone help me clear my doubt.

I think it should be the logic, initially total length of the train couldn't on platform. It takes 20 sec (reference point where the man stand) to be on platform completely. From that reference point only the train completely travels on platform. That why we are subtracting the time 36-20=16sec it is the time train completely on platform.

Now calculate length = (54*5/18) *16 sec = 240 sec.

Friends. Am I correct?