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.

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.

Hi, Chandana asked why don't we add the length of the train. Well this is a common doubt everybody gets .

Now you think, both are travelling in opposite direction.

Eg:

Train1 --------------> Fastest train

<---------------Train2. Slowest train

When this is the case the train1 and train2 travel with their respective speed. There will be no collision rigth because they travel in opposite direction. So we take only one length of the train that too the train we respect to .ie here we take the slower train which is 500 mts length.

Hope you got it. Have a nice day!

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

So, please explain in detail.

Can someone explain why they reversed the distance in the final calculation (i.e 125/6 to 6/125)?