Question
A boat can cover 72 km in still water and 60 km in
downstream in 4 hours and 3 hours respectively. Find the time taken by the boat to cover 60 km upstream and 70 km downstream.Solution
Speed of the boat in still water = 72/4 = 18 km/h Downstream speed of the boat = 60/3 = 20 km/h Speed of the stream = 20 – 18 = 2 km/h Upstream speed of the boat = 18 – 2 = 16 km/h Time taken to cover 60 km upstream and 70 km downstream = 60/16 + 70/20 = 3.75 + 3.5 = 7.25 hours
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