Aptitude - Problems on Trains - Discussion

The answer is 48sec since to cross the driver of the faster train you have to travel the length of the faster train plus the length of the slower train since the driver of the faster train will be sitting at the front of the train.

So.

Relative speed = 45 + 30 = 75kmph.
Converting to m/s = 75 * 5/18 = 125/6 m/s.
Time taken = (500 + 500) * 6/125 = 48 sec.

Answer should be 48.

I think the right answer is 48 sec.

@Pinku.

i.e 24sec. Isn't it logical?

If faster train crosses slower train in 24 sec. Do you think the slower train is still not done crossing? Whether a faster train crosses a slower train same time is taken for the slower train to cross a faster train. Because they are crossing each other. If the faster train is done crossing the slower train. Then it means the slower train is also done crossing. These are the logical and physical reality. Especially a same length train or object moving in the opposite direction.

@All.

I am also confused about the 500, but we need to carefully read the question; they mentioned that the slower train crosses the driver, not the faster train.

Correct me, if I am wrong.

Yes, the right answer is 48 sec.

No, it is not 48 sec, Check It's mentioned to find the time to cross the fast train driver, so consider this as point or pole example and solve using the length of a single train.

Won't the driver be facing each other at the start? Hence time taken is 0. They are already facing each other or at the same spot at start of the problem.

Simple:
Opposite direction (ADD the speed).

45 + 30 = 75 "answer asked in sec then convert it by multiplying 5/18 to 75".

Speed is 125/6 m/sec.
Now distance travelled by each train is its own distance and other train distance,
i.e. 500+500 =1000.
We have speed and distance use the time formula.
T = D/S.
= 1000 * 6/25.

Here it states to cross the driver, not cross the train.

So, please explain in detail.