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Train problems

Point to remember:
  • Time taken by a train x metres long in passing a signal post or a pole or a standing man is equal to the time taken by the train to cover x metres.
  • Time taken by a train x metres long in passing a stationary object of length y metres is equal to the time taken by the train to cover x+y metres.
  • Suppose two trains are moving in the same direction at u kmph and v kmph such that u>v, then their relative speed = u-v kmph.
  • If two trains of length x km and y km are moving in the same direction at u kmph and v kmph, where u>v, then time taken by the faster train to cross the slower train = (x+y)/(u-v) hours.
  •  Suppose two trains are moving in opposite directions at u kmph and v kmph. Then, their relative speed = (u+v) kmph.
  •  If two trains of length x km and y km are moving in the opposite directions at u kmph and v kmph, then time taken by the trains to cross each other = (x+y)/(u+v)hours.
  •  If two trains start at the same time from two points A and B towards each other and after crossing they take a and b hours in reaching B and A respectively,       then A's speed : B's speed = (√b : √a)
  • Speed of Train = ( Sum of the length of two trains ) / Time taken
  • Time taken to cross a stationary Engine = (Length of the train + Length of engine) / Speed of the train .
  •  Time taken to Cross a signal Post = Length of the train / Speed of the Train

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