Speed of the train relative to man
= (125/10) m/sec = (25/2) m/sec.
[(25/2) x (18/5)] km/hr = 45 km/hr.
Let the speed of the train be 'x' km/hr.
Then, relative speed = (x - 4) km/hr.
x - 4 = 45 => x = 49 km/hr.
Given that train K crosses a pole in 30 seconds and train L crosses the same pole in one minute and 15 seconds.
Let the length of train K be Lk and that of train L be Ll
given that Lk = 3/4 Ll
As the train K and L crosses the pole in 30 seconds and 80 seconds respectively,
=> Speed of train K = sk = Lk/30
Speed of train L = sl = Ll/80
Lk = 3/4 Ll
=> sk = 3/4 Ll/(30) = Ll/40
Ratio of their speeds = sk : sl
= Ll/40 : Ll/80
=> 1/40 : 1/80 = 2 : 1
Relative speed = (72 - 36) x 5/18 = 2 x 5 = 10 mps.
Distance covered in 32 sec = 32 x 10 = 320 m.
The length of the faster train = 320 m.
Let the speed of the faster train be 'X' kmph,
Then their relative speed= X - 48 kmph
To cross slower train by faster train,
Distance need to be cover = (400 + 600)m = 1 km. and
Time required = 180 sec = 180/3600 hr = 1/20 hr.
Time = Distance/Speed
=> 1/20 = 1/(x-48)
X = 68 kmph
Let the length of each train be x mts.
Then, distance covered = 2x mts.
Relative speed = 36 - 26 = 10 km/hr.
= 10 x 5/18 = 25/9 m/sec.
2x/36 = 25/9 => x = 50 mts.
Relative Speed = 60 -40 = 20 x 5/18 = 100/18
Time = 50
Distance = 50 x 100/18 = 2500/9
Relative Speed = 60 + 40 = 100 x 5/18
Time = 2500/9 x 18/500 = 10 sec.
Here total distance = 154 + 101 = 255 mts
Given speed = 120 kmph = 120x5/18 m/sec
Hence, Time = d/s = 255x18/120x5 = 7.65 sec
Total distance = 150 + 210 = 360 mts
Time taken to cross each other when moving in opposite direction = 10.8 sec
Relative speed of trains = (350/10.8) x 18/5 = 3600/30 = 120 kmph
Speed of shorter train = (150/12) x 18/5 = 45 kmph
Hence, speed of longer train = 120 - 45 = 75 kmph.
Speed = 108 km/hr
enter a tunnel,, means that the train covers a distance equal to its own length
so (108 x 5/18) = x/4 where x= length of train
hence x = 120 mtrs
to pass completely train has to travel a distance = (x + tunnel length) that is 1120 mtrs.
so (1120/t) = (108x5/18)
t = 37.33 sec
Next train comes at 17:00 hrs.
So, last train will be = 17:00hrs - 2:30hrs
= 14:30hrs
Announcement made after 37 min of the last train.
S0, 14:30hrs + 00:37 min
= 15:07 hrs.
The distance to be covered = Sum of their lengths = 200 + 300 = 500 m.
Relative speed = 72 -36 = 36 kmph = 36 x 5/18 = 10 mps.
Time required = d/s = 500/10 = 50 sec.
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