1.

A Train Overtakes Two Persons Walking Along A Railway Track. The First One Walks At 4.5 Km/hr. The Other One Walks At 5.4 Km/hr. The Train Needs 8.4 And 8.5 Seconds Respectively To Overtake Them. If Both The Persons Are Walking In The Same Direction As The Train? So What Is The Speed Of The Train ?

Answer»

Convert the Speed in m/sec

so 4.5 km/hr = ( 4.5 x 5/18 ) m/sec = 5/4 m/sec = 1.25 m/sec,

and 5.4 km/hr = ( 5.4 x 5/18 ) m/sec = 3/2 m/sec = 1.5 m/sec.

Here ASSUME the speed of the train as x m/sec. 

so relative will be (x-1.25) and (x - 1.5) 

(x - 1.25) x 8.4 = (x - 1.5) x 8.5

=> 8.4x - 10.5 = 8.5x - 12.75

=> 0.1x = 2.25 

=> x = 22.5 m/s

As OPTIONS are GIVEN in km/hr so convert the speed mps to KMPH

So Speed of the train = ( 22.5 x 18/5 ) km/hr = 81 km/hr.

Convert the Speed in m/sec

so 4.5 km/hr = ( 4.5 x 5/18 ) m/sec = 5/4 m/sec = 1.25 m/sec,

and 5.4 km/hr = ( 5.4 x 5/18 ) m/sec = 3/2 m/sec = 1.5 m/sec.

Here assume the speed of the train as x m/sec. 

so relative will be (x-1.25) and (x - 1.5) 

(x - 1.25) x 8.4 = (x - 1.5) x 8.5

=> 8.4x - 10.5 = 8.5x - 12.75

=> 0.1x = 2.25 

=> x = 22.5 m/s

As options are given in km/hr so convert the speed mps to kmph

So Speed of the train = ( 22.5 x 18/5 ) km/hr = 81 km/hr.


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