Aptitude - Problems on Trains - Discussion

I did not understand how you got 50/3? Please I need a clear explanation.

25/3 + 25/3 = 50/3 i.e. 3 being a common denominator.

@Mounika.

We supposed the speed of the first train = x.

Nd speed of the faster train which is moving twice as fast the other = 2x (as we have given).

Now, given length of each train = 100m,

Time = 8sec,

Substitute these value in formula.

Time = (distance/speed).

8sec = (100+100/x+2x).

"Here we are adding the values b'coz the trains are in opposite direction with each other, which you can easily understand by reading the formula column. ".

8 = 200m/3x.

By cross multiplication.

24x sec = 200m.

x = 200/24.

x = 25/3 m/sec.

When we convert it into km/hr it becomes.

x = 30km/hr but.

Acc. To question they are asking for faster train which is 2x.

So by putting the value of x in 2x we'll get the correct answer.

2(30km/hr).

Answer = 60 km/hr.

What 50/3 I didn't understand this step?

Hi @Raja,

5/18 is to convert KM to Meters.

18/5 is to convert Meters to KM.

As, in question it is given in Meters but answer is in meters so have to convert Meters to KM. So we are using.

What is 18/5 and 5/18 ? why we are using please explain?

Here there is no need of finding relative speed right? then why we find relative speed?

How did you reversed the 18/5 and multiplied with 50/3?

Here there is no need of finding relative speed right? then why we find relative speed?

Relative speed = (x+y);
x = x;

y = Twice faster than 'x', So 2x;
y = 2x;

Relative speed = (x+2x) = 3x.