Aptitude - Problems on Trains - Discussion

What to do if asked length of a slower train? Anyone, please explain to me.

Why we don't count two train lengths? Anyone explain me.

@Siddarth.

You don't need to divide 250/9 completely because we don't need the answer in decimals according to the options.

You should divide 250 by 9 until you cannot divide it further without the need of a decimal i.e. when the quotient is 27 and the remainder is 7.

And then you can write it in the form of a mixed fraction i.e. quotient remainder/divisor or 27 7/9 as given in option C.

Can someone explain why we take 5/18 in the km/hr? I am not getting it.

Please, explain this how 250/9 to 27 * 7/9?

@Dwivedi.

Here what they asked is, the length of the faster train.

If you want the length generally we multiply speed and time.

In this question, you think that you are in a slower train it's speed is 20kmph in which ever the place either in front middle or in last your speed is 20kmph. The faster train has to cross you so the speed of train relative to you is 20kmph or 50/9mps.

Length of the faster train = relative speed in mps*time in sec = 50/9 * 5 = 250/9 = 27 * 7/9.
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The question focus on the fast train and the man sitting somewhere in the train.

Here we can consider the slow train as a man running with 20km/hr.

So now the question can be understood in this way as well:.

There is a train running at speed of 40km/hr and a man running with 20km/hr in the same direction of the train. Calculate the length of the train?

Now solve it. Hope now it will become easy for everyone.

250 /9 = 27.777777778 means then how to convert it into 27*7/9?

Please explain in detail.

Simple method.

Speed =distance/time.
Relative speed (if same direction)=s1-s2.
Consider usefull formula s1-s2=(l1+l2)/time.
Here l1= trian 1 length= x meters.
L2= 0 meters ( person who is sitting in train),
Time taken to cross person is t=5 sec,
40-20 km/h = x/5,
20km/h =x/5,
20*5/18 =x/5,
(50/9)*5 =x,
250/9=x,
27.77 => answer.

We can't find the slower train length as it will never pass the faster train.

So in order two find slower train length we need how much time the faster train take to pass the slower train not the man.

Relative means that slower is still.