Help him or he will die!
A man was walking on a bridge. When he passed 3/8 of it ,He heard a train horn coming from the side he had came from. The train was moving 60 km/h. if the man moved with velocity x, The train will hit him at the end of the bridge. If he moved with the same velocity, x, in the opposite way (towards the train) the train will hit in the beginning of the bridge. Find X
The answer is 15.
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1 solution
time = distance/velocity
the time that the train will take to reach a is: (D/60) ===>(1)
the time that the train will take to reach b is: [(D+L)/60]==> (2)
the time that the man will take to reach a is: [(3L/8)/x]===>(3)
the time that the man will take to reach b is: [(5L/8)/x]===> (4)
the train will hit the man at a if the man moved with velocity x so [(3L/8)/x] = (D/60) ===> (5)
the train will hit the man at b if the man moved with velocity x so [(D+L)/60] = (5L/8)/x]==> (6)
from (5) (180L/8) = xd
from (6) (300L/8) = xd + xL
300L/8 = (180L/8) + xL
300/8 = 180/8 + x
x = 15