Number System - Boats & Streams


  1. In water, the direction along the stream is called Downstream. And the direction against the stream is called Upstream.

  2. If the speed of the boat in still water is u km/hr and the speed of the stream is v km/hr, then:

    1. Speed downstream = (u + v) km/hr

    2. Speed upstream= (u - v) km/hr

  3. If the speed downstream is a km/hr and the speed upstream is b km/hr, then:

    1. Speed in still water = 1/2 (a + b) km/hr

    2. Rate of the stream = 1/2 (a - b) km/hr

  4. When the distance covered downstream and upstream are equal, we can write: (u + v)t1 = (u - s)t2 where t1 and t2 are different time taken.

Solved Examples

Solved Examples