Aptitude - Problems on Trains - Discussion

If these two trains are moving in opposite direction then how can we add their distance.

Here I wanna know! how we suppose to have 2x as fast train. Can any one suggest me"""If one is moving twice as fast the other""". And what about this?

Hi seema rules wise we have to add the distance, relative speed based on the direction of both trains (same:-, opposite:+).

Assume one train is moving with X speed than other is twice faster it means 2x

look normal speed =x
twice the above speed=2*x=2x

I didn't understood how can I clear this problem?

I don't understand please explain it brief.

Now study the problem carefully the given data is
two trains moving in opposite direction . that means we add them 100+100=200mts

to cross these 200mts it takes 8 secs ok
now, they have asked to find the speed of the faster train if the speed is twice the slower train , this is given in the question.

Now ,

speed=distance/time

speed=200mts/8secs ok
as options are given in km/hr , we have to convert speed to km/hr

So we multiply with 18/5
well (200mts/8secs)*18/5=(200/8)*(18/5)=90km/hr
these is the total speed .

Now they asked us to find the speed of the train twice the other train

Let the speed of first train =xkm/hr

Speed of other train should be twice=2x km/hr

So we have got total speed as 90km/hr
x+2x=90km/hr
3x=90km/hr
x=30km/hr
speed of one train is 30km/hr.

So they asked twice the speed of train

So we get 2x=2*30
=60km/hr
Now if we add 30+60=90km/hr

We got the total speed

The speed of the faster train is 60 km/hr

In this problem how we can take 50/3?

When the train is Opposite direction, than the relative speed is add to both (100+100)= 200

Give me short cut.