Time & Distance, Trains, Boats & Streams Tricks and Formulas

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Time & Distance

Suppose a man covers a distance at ‘x’ kmph and an equal distance at ‘y’ kmph, and then average speed during his whole journey is kmph

Lengths of trains are ‘x’ km and ‘y’ km, moving at ‘u’ kmph and ‘v’ kmph in the same direction, then the time taken y the over-taker train to cross the slower train is hrs
Time taken to cross each other hrs
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.

If the speed of a boat in still water is and the speed of the stream is v , then: . and

If the speed downstream is a km ⁄ hr and the speed upstream is b km ⁄ hr, then: Speed in still water . and Rate of stream km ⁄ hr.