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Aptitude Day 251

Boats and Streams

Rules to be followed:

  • The direction along the stream in water is called downstream and the direction against the stream is called upstream.
  • If the speed of a boat in still water is u km/hr and the speed of the stream is v km/hr, then:
                    Speed of the downstream = u+v km/hr.
                    Speed of the upstream = u-v km/hr.
  • If the speed of the downstream is a km/hr and the speed of the upstream is b km/hr, then:
                       Speed in still water = 1/2(a+b) km/hr.
                       Rate of the stream = 1/2(a-b) km/hr.

A Problem on Boats and Streams:

1. In 1 hour, a boat goes 9km along the stream and 3km against the stream. The speed of the boat in still water (in km/hr) is:
Solution:
                  Speed in still water = 1/2[9+3] 
                                                 = 6 km/hr.



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