Distance covered upstream in 30/4 minutes = 1/4 Km Distance covered upstream in 1 hour = 1/4× 4/30× 60 = 2 km/hr Distance covered downstream in 5/2 minutes = 1/4 km Distance covered downstream in 1 hour = 1/4 × 2/5× 60 = 6 km/hr Speed of the man in still water = 1/2(2 + 6) = 4 km/hr