Aptitude - Problems on Trains - Discussion

@Randhir

I too not getting tht 6y concept..pls explain me...

I dint get how x-1 term is used.

According to this problem first we have to consider that both trains A & B are start at same time then only we can arrive the answer.

In question it is given that, A train starts at 7 a.m. and B train starts at 8 a.m.

Let starting time for A train = x
and starting time for B train = x-1 .

@Nayana,

We know that distance= speed*time

So, distance = y*6 = 6y

Calculate time between 5pm and 11pm, so totally 6 hours.

Thanks.

@Easwar

The speed of one train is twice the other so let
speed of 1st train is Y.
speed of 2nd train is 2Y.
then distance between point A and B is 6Y.

Suppose they meet x hours after 5 a.m.

Distance covered by 1st train in X hours = YX km.

Distance covered by B in (X - 2) hours = 2Y(X - 2) km.

Therefore YX + 2Y(X - 2) = 6Y

=> YX + 2YX - 4Y = 6Y

=> 3YX = 10Y

=> X =10 / 3 (in hours)
=> X =10/3*60 (because converting into minutes)
=> X =200 minutes
200 minutes means 3 hour 20 minutes

So, they meet at 8 : 20 p.m.

Hii Randhir How come distance between point A and B is 6Y? Please explain.

@Gayatri, nithi, nayana


Speed=distance/time

1st train leaves a point A at 5 p.m. and reaches another point B a 11 p.m.that means time taken by train 6 hours.
Time = 6 hour

Speed of the 1st train is Y
Speed = Y km/h

Distance= speed*time (because speed=distance/time)
Distance= Y * 6 = 6Y

if you are still not getting my point then comes to train 2nd
2nd train leaves point B at 7 p.m. and reaches point A at 10 p.m. that means time taken by train 3 hours.
Time = 3 hour

Speed of the 1st train is 2Y
Speed = 2Y km/h

Distance= speed*time (because speed=distance/time)
Distance= 2Y * 3 = 6Y

How x=3 is converted into 10, please tell me any one.

3 = 3 hour.....therefore 7 a.m + 3 hour = 10 a.m

Actually I didn't understand this problem how do you get 10 AM as answer please would anyone get rid of these problem am not getting it.

One more easy method to solve such problems.
Given that distance between two stations is 110km.
First trains speed is 20kmph and starts at 7 am
2nd trains speeed is 25kmph and starts at 8 am.

So at 8 am, the distance covered by first train is 20 kms.
Now remaining distance to cover is (110-20 = 90 km).

The relative speed of both the trains is 20+45 = 45 kms.
So it will take 2 hours to cover 90 km.
Hence the trains will meet after 2 hours from 8am i.e. at 10 am.