Question
A ship covers a distance of 240 km downstream in a time
that is 2 hours shorter than the time it takes to cover the same distance upstream. The ship's upstream speed is 60% of its downstream speed. The task is to calculate the speed of the ship in still water under these conditions.Solution
ATQ; Let the downstream speed of the ship be ‘a’ km/h and upstream speed of the ship be ‘0.6a’ km/h then, (240/a) + 2 = (240/0.6a) Or, (400/a) – (240/a) = 2 Or, 160 = 2a So, a = 80 So, upstream speed of the ship = 0.6a = 48 km/hr Downstream speed of the ship = a = 80 km/hr Since, speed of ship in still water = {(downstream speed + upstream speed)/2} So, speed of the ship in still water = (80 + 48)/2} = 64 km/hr
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