Question

Two trains moving in the opposite direction and their speeds in the ratio 4:13.The first train passing a standing man in 13.25 seconds and another in 9 seconds. The time taken to cross each other is

Answer 1

Ratio of speeds of two trains = 4:13

Let their speeds be 4x and 13x

First train crosses the standing man in 13.25 sec.

We know that,

Speed = Distance / Time

When a train passes a standing man, distance covered is equal to the length of the train.

Length of first train = Speed * time

= 4x * 13.25

= 53x mts

Second train crosses the standing man in 9 sec.

Length of second train = 13x * 9

= 117x mts

When two trains crosses each other,

Total distance = Sum of lengths of two trains

= 53x + 117x

= 170x mts.

Relative speed of trains = Sum of speeds of both trains

= 4x + 13x

= 17x m/sec

Time taken to cross each other = Distance / relative speed

= 170x / 17x

= 10 sec

Hence, two trains will cross each other in 10 seconds.