# Important Formulas

1. Speed = Distance / Time

So Distance= Speed X Time and

Time = Distance / Time

2. Conversion of Km/hr to m/sec :

m km/hr = m X (5/18)

3. Conversion of m/Sec to Km/hr :

m m/sec = m X (18/5)

4. When a train crosses a single post or standing man or a tree, the train will move a distance equal to the length of the train. So the time time taken by the train on those situation is = (Length of the train)/(Speed of the train)

5. When a train need to cross a platform or a bridge, the train have to cross the distnace equal to the sum of the length of the train and bridge. So the Time taken by the train to cross a platform or bridge =

Length of Train + Length of Platform(Bridge) / Speed of Train

6. If two trains (or a train and an object ) of length a
meters and b meters move in the **same direction** with the
speed of X m/s and Y m/s respectively, where X>Y then their
relative speed is = (X-Y) m/s and Time time taken the fater
trains to cross the slower train is =

(a + b) / (X-Y)

7. If two trains (or a train and an object ) of length a
meters and b meters move in the **opposite direction** with the
speed of X m/s and Y m/s respectively, where X>Y then their
relative speed is = (X+Y) m/s and Time time taken to cross
each other is =

(a + b) / (X+Y)