Aptitude - Problems on Trains - Discussion

In this solution how you are multiplying 5/18 with 200.

I can't understand that wll you please explain me that.

Why there is (x+270)/9 acc. to formula (270+x)/500/9 = 9 right?

Relative speed should be minus from each train speed because the direction is opposite, isn't it so?

Always opposite will add and same will be subtract.

I want to know one thing usually where we use or apply this relative speed concept ?

@Janani.

The concept of relative speed is still the basic time, speed and distance formula applied to distance between two moving bodies.

In a simple case of the distance.

Formula, a body traveling with a speed of 50 km/h is reducing the gap between its starting point and the finish point by 50 km every hour.
&
In the relative speed case of the distance formula two moving bodies, traveling at a relative speed of 50 km/h towards/away from each other, are reducing/increasing the gap between them by 50 km every hour.

Hope this help.

Easy way.

270 + x
---------------- = 9.
33.33+22.22

x = 499.5 - 270.

x = 229.5.

Can anyone please tell me when to add or subtract the given relative speeds.

How to find that this problem is need to convert km/hr to m/s or m/s to km/hr. Please explain?

If the two trains cross opposite directions both are cross each other. So we need calculate crossing speed of the two trains. So we must add two trains speeds respectively. We assumed train A cross train B in a particular amount of speed as same as Train B also cross Train A.

Here two respective speeds are happen then only the process completed in a particular Time. Or we assume Train A is stable that time train B only cross Train A that is Train A speed is zero this is the logic I hope now you can understand.