Question
The speed of a boat in still water is 15 km/hr. If the
boat covers 120 km in upstream in 12 hours, then find the time taken by the boat to travel 120 km in downstream.Solution
Let the speed of the boat in still water and the speed of the current be ‘x’ km/hr and ‘y’ km/hr, respectively Upstream speed of the boat = (x – y) = 120/12 = 10 km/hr Or, 15 – y = 10 Or, y = 15 – 10 = 5 km/hr Therefore, downstream speed of the boat = 15 + 5 = 20 km/hr Required time taken = 120/20 = 6 hours
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