# Time Speed Distance

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## Basic formulas - Time Speed and Distance

1) Distance = Speed × Time

2) Converting Km/hr to m/sec 3) Converting m/sec to Km/hr 4) If ratio of speeds is a:b then the ratio of distance covered in the same time is a:b.

5) If ratio of speeds is a:b then the ratio of time taken to cover the same distance is b:a.

6) If half of the distance is covered at a speed of a Km/hr and the other half at a speed of b Km/hr then the average speed for the entire journey is Km/hr. (Shortcut 1)

7) If an object travels for half of the time at a speed of a Km/hr and the other half of the time at a speed of b Km/hr then the average speed for the entire journey is Km/hr. (Shortcut 2)

### Concept of TRAINS

8) Time taken by a train of length L meters, travelling at a speed of S m/sec to cross a pole/a standing man is 9) Time taken by a train of length L meters, travelling at a speed of S m/sec to cross a platform or a standing train or a bridge of length x meters is 10) Time taken by a train of length L1 meters, travelling at a speed of S1 m/sec to cross another train of length L2 meters, travelling at a speed of S2 m/sec in the same direction is 11) Time taken by a train of length L1 meters, travelling at a speed of S1 m/sec to cross another train of length L2 meters, travelling at a speed of S2 m/sec in the opposite direction is ### Concept of STREAMS

Let S be the speed of the stream and B be the speed of the boat in still water.

12) Upstream means against the stream (Moving in the direction opposite to the stream). Speed upstream = B - S

13) Downstream means with the stream (Moving in the direction of the stream). Speed downstream = B + S