Aptitude - Problems on Trains - Discussion

Distance = time * speed 125 = 10 * speed
distance/time = speed 125/10 = (25/2)m/s = speed
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Answer should be in km/hr so convert m/s
km = 1000m and hr = 3600s
m = km/1000 and s = hr/3600
m/s = (3600/1000)km/hr
m/s = (18/5)km/hr
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The condition was speed = (25/2)m/s
= (25/2)(18/5)km/hr
= 45 km/hr
The speed was relative to man so we have taken time in consideration of man
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See further in in view answer.
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I could not understand this problem is there any way to understand this more easily.

1km=1000m.
1hour=3600sec.

So to convert from km/hr to m/sec, we need to divide 3600/1000 i.e,.

1km/1hr=3600s/1000m which is equal to 18/5.

If it was asked to convert m/s to km/hr then it would be 1000m/3600s= 5/18

18/5 = 1 km/hr = 1000/3600 m/s

= 10/36 m/s

= 5/18 m/s.

Please explain 18/5.

Answer = 45 km/hr is relative speed of the train.

Now, you calculate (u-v).

The Speed of the train 50 km/hr answer is correct.

Yeah superb.

If someone feel difficult to understand 5/18 i.e; m/s

To convert kmph to mps 1000/60*60 m/s

It is same thing.

Nice explanation.Thanks.

Hai Madhu N Swathi,
****When two bodies say x km/hr and y km/hr are moving in the same direction then their relative speed is (x-y) km/hr
****When we want to convert km/hr in to m/s we multiply with 5/18.
*** Let the speed of the train be x kmph
Speed of the train relative to man(x-5)kmph
(x-5)*5/18
now as we know that Distance/speed=time
now,speed is (x-5)*5/18;
distance is 125m;
time is 10 sec;
now u vl get the answer
***********