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Discussion :: Boats and Streams

  1. What is the speed of the boat in still water?

    I. The speed downstream is 12 kmph.

    II.The speed upstream is 4 kmph.

    III.In a to and fro journey between two points, the average speed of the boat was 6 kmph.

  2. A.

    I and II only

    B.

    All I, II and III

    C.

    III, and either I or II

    D.

    Any two of the three

    E.

    None of these

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    Answer : Option D

    Explanation :

     

    From I and II, speed of boat in still water = 1 (12 + 4) km/hr = 8 km/hr.
    2

     

    From II and III, we get:

     

    Using average speed=\(\frac { 2XY } { X+Y } \),we get:\( \frac { 2*4*Y} {4+Y} =6\)

     

     y = 12.

     

     Required speed =\(\frac { 1 } { 2 }\)(12 + 4) km/hr = 8 km/hr.

     

    Similarly, I and III also give the answer.


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