(A) 3 Km/h
(B) 4 Km/h
(C) 5 Km/h
(D) 8 Km/h
Correct Option is: C
Rate upstream = (1500 / 1350) m/s = (150/135) m/s
= 10/9 m/s
Rate downstream = (1500 / 900)m/s = (15/9)m/s
= 5/3 m/s
Rate in still water = ½ [ a+ b]
= ½[10 / 9 + 5 /3]
= ½[10 +15 / 9]
= ½[25/9]
= 25/18 m/s
= (25/18) * (18/5)km/hr
speed in still water = 5 km/hr