Aptitude - Problems on Trains - Discussion

Where did you get 5/18? Explain me. It is confusing.

With these explanations and doubts clear all my doubts.

Thanks to every one.

Easiest process:

Let, length = x m.

Speed of 1st mvng train = 46 * (5/18) = 115/9 m/sec.

""slow"" = 36 * (5/18) = 10 m/sec.

Formula = time is taken by a first moving train to overtake (same direction) a slow moving train = (length of first moving train + length of slow moving train) / (speed of first moving train - speed of slow moving train).

Hence 36 = 2x / ((115/9) - 10) 2x is taken because both lenght are equal.

Hence, x = 50m.

In other words, we can say that in this question slowest train is at rest and fast train in moving with speed of 10 km/hr and to pass slow train fast train only needs to pass it's length because both trains start at same point so the distance covered by train in 36 sec is,

10 * (5/18) * 36 = 100m.

So the correct answer is 100 not 50m.

When both trains start from same point and one passes another then we should take distance x m, not 2x metre. This condition is possible when fast train is behind the slow train.

Well explained. Thanks.

(X1 + x2/u - v) = 36sec. Formula x1, x2 = x.
(2x/ 46 - 36) = 36sec.
(2x/10) = 36sec.
(10 * 5/18) = (25/9).
(2x/36sec) = (25/9).
2x = 100m.
X = 50m.

After relative speed one have '0' and other '10kmph'.

Then,
-----------> <=1st train with 46kmph relative speed is '10 kmph.
-----------> <=2nd train with 36kmph relative speed is '0' kmph.

After passing,
-----------> <=with relative speed '10' kmph.
-----------> <=with relative speed '0' kmph.

So only one train length speed to be calculated, then why it take "2x"?

Please explain.

I have a doubt, hear if two trains are same length and same direction in that faster train speed 10km/h more then slower train in this case the faster train speed only 10km/h only and it crossed in slower train in 36 seconds that means faster train speed more then (25/9) m/s.

And they mentioned faster train takes 36sec to cross the slower train that means.

According to formula length = speed * time.

(25/9) * 36 = 200m.

The actual length of the train = 200m.

I think none of the above option is the answer.

Faster train 46 km/hr, and small train 36 km/hr then, 46 - 36 = 10 km/hr.
Then, 10 * 5/18 = 25/9.

It crosses 36 seconds then 36 * 9/25 = 12.96m then how it becomes 50 m?

I am confused. please explain