A man rows 750 m in 675 seconds against the stream and returns in 7 and half minutes. His rowing speed in still water is
Answer: B
Rate upstream = (750/675) = 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) × (18/5) kmph
= 5 kmph