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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

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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