Question
A boat can cover 60 km in still water and 75 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 = 60/4 = 15 km/h Downstream speed of the boat = 75/3 = 25 km/h Speed of the stream = 25 – 15 = 10 km/h Upstream speed of the boat = 15 – 10 = 5 km/h Time taken to cover 60 km upstream and 70 km downstream = 60/5 + 70/25 = 12 + 2.8 = 14.8 hours
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