Question

The speed of two trains are in the ratio 6:5 they are running in opposite direction on parallel tracks if each takes 2 secs to cross a pole .how many time will they take to cross each other

Answer 1

Let the speed of the trains be 6x and 5x respectively.

∴ Relative Speed of the trains = 6x + 5x
 = 11x

According to the Question, Both the trains cross the pole in 2 seconds.
∴ Length of the First train = 6x × 2
   = 12x
Also, Length of the second train = 5x × 2
  = 10x

∴ Total length of both the trains while crossing the Pole = 12x + 10x
  = 22x 

Now, Using the Formula,

 Speed = Distance/Time
∴ Time = (Total Length)/Relative Speed
⇒ Time = 22x/11x
∴ Time = 2 seconds.


Hence, the time which the trains will take to cross each others is 2 seconds.


Hope it helps.

Answer 2

Let x be any variable
So,
Let us consider the speeds of the trains to be 5x and 6x respectively

Now, the two trains cross the pole in 2 seconds 
So,
Length of first train =(Velocity*Time)
                                =6x * 2
                                 =12x

Length of first train =(Velocity*Time)
                                =5x * 2
                                 =10x

The total length of the two trains will determine the distance required to be covered
So,
Total distance to be covered is 
10x+12x
=22x

The relative speeds of the trains will be equal to
=6x+5x
=11x

Because the two trains are running against each other to parallel
So,
Time required=(Total distance covered /Relative velocity)
                       =22x /11x
                       =2
So the time required to cross each other will be 2 seconds