Boats & Streams

In this type of problems, you will be given the speed of boat in still water and the speed of stream. You have to find the time taken by boat to go upstream and downstream.
Let U= Velocity of the boat in still water
V=Velocity of the stream.
T = Time taken
·       While moving in upstream, distance covered, S=(U−V)T

·       In case of downstream, distance covered ,S=(U+V)T 
         ·       If the speed downstream is a km/hr and the speed upstream is b km/hr, then:
Speed in still water    =½

(a + b) km/hr.

                                           Boats and Streams Shortcut Methods

        Rate of stream =½

(a - b) km/hr.

                                          Boats and Streams Shortcuts
Example:
In one hour, a boat goes 11 km/hr along the stream and 5 km/hr against the stream. The speed of the boat in still water (in km/hr) is

Explanation:
Speed in still water =
1
(11 + 5) kmph = 8 kmph.
2

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