Answer with Explanation:
Assume three-quarters of a kilometre as 750 metres,and 11 minutes as 675 seconds.
Rate upstream = (750/675) m/sec = 10/9 m/sec.
Rate downstream = (750 /450) m/sec = 5/3 m/sec.
Rate in still water = 1/2 (10/9 + 5/3) m/sec
= 25/18 m/sec
= (25/18 x 18/5) km/hr
= 5 km/hr.
Assume three-quarters of a kilometre as 750 metres,and 11 minutes as 675 seconds.
Rate upstream = (750/675) m/sec = 10/9 m/sec.
Rate downstream = (750 /450) m/sec = 5/3 m/sec.
Rate in still water = 1/2 (10/9 + 5/3) m/sec
= 25/18 m/sec
= (25/18 x 18/5) km/hr
= 5 km/hr.