Tips & Tricks GIVEN: The boat covers 15 km upstream in 5 hours and 24 km downstream in 4 hours FORMULA USED: If ‘D’ and ‘U’ are the Downstream and Upstream speeds: Speed of boat in still water = (D + U)/2 Speed of current = (D – U)/2 CALCULATION: According to the question, Downstream speed = 24/4 = 6 km/h Upstream speed = 15/5 = 3 km/h ∴ Speed of the Boat in still water = 1/2 × (6 + 3) = 4.5 km/h