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

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Time & Distance

Suppose a man covers a distance at ā€˜xā€™ kmph and an equal distance at ā€˜yā€™ kmph, and then average speed during his whole journey is kmph


  • Lengths of trains are ā€˜xā€™ km and ā€˜yā€™ km, moving at ā€˜uā€™ kmph and ā€˜vā€™ 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.

Boats & Streams

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 ā„ hr and the speed upstream is b km ā„ hr, then: Speed in still water . and Rate of stream km ā„ hr.