A man can row three - quarters of a kilometer against the stream in 11¼minutes. The speed(in km/hr) of the man in still water is Choose the correct choice.
A) 2  B) 3  C) 4  D) 5  E) 6
Solution   Rate upstream	= (750 / 675)m/sec   = (10 / 9) m/ sec.   Rate downstream	= (750 / 450)   =(5 / 3) m/sec   Rate in still water	= 1/2(10 /9 + 5/3)   = (25/18x18/5)km/hr   = 5 km/hr.   Answer 5
<result>D</result>
A man can row three - quarters of a kilometer against the stream in 11¼minutes. The speed(in km/hr) of the man in still water is