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Discussion :: Boats and Streams

  1. A man can row three-quarters of a kilometre against the stream in 11 minutes and down the stream in 7 minutes. The speed (in km/hr) of the man in still water is:

  2. A.

    2

    B.

    3

    C.

    4

    D.

    5

    View Answer

    Workspace

    Answer : Option D

    Explanation :

    We can write three-quarters of a kilometre as 750 metres,

    and 11 minutes as 675 seconds.

    Rate upstream=\([ \frac { 750 } { 675 }]m/sec\)=\(\frac { 10 } { 9 }m/sec\)

     

    Rate downstream =\([ \frac { 750 } { 450 }]m/sec\)=\(\frac { 5 } {3}m/sec\)

    =\(\frac { 25 } {18}m/sec\)

    =[\(\frac { 25 } {18}*\)\(\frac {18} {5}\)]km/hr

     = 5 km/hr.


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