Question

Two trains each of length 350 m are running in the opposite directions with velocities 54 km/h and 72 km/h. In what time they will completely cross each other?​

Answer 1

Relative speed = 72 + 108 = 180 km/hr

Length of both train = 180 × (5/18) × 10 = 500 m

Length of train = 500/2 = 250

Time taken to cross platform = (250 + 350)/72 × 5/18 = 30 sec.

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Answer 2

Given,

Length of the train=350m

Running in opposite direction with velocities 54km/h and 72km/h

To Find,

Time when they will cross each other.

Solution,
First we have to find out the relative speed between the two trains.

So, relative speed = 72 -(-108) = 180 km/hr.(negative sign is for opposite in direction)

Then, Length of both train = 180 × (5/18) × 10 = 500 m

Length of train

= 500/2 = 250m

Then, Time taken to cross platform

= (250 + 350)/72 × 5/18 = 30 sec.

Hence, in 30 secs they will completely cross each other.