Question
A boat takes 18 hours to cover 216 km upstream and 12
hours to cover the same distance downstream. Find the time taken by the boat to cover 180 km in still water.Solution
Upstream speed of the boat = 216 ÷ 18 = 12 km/h And downstream speed of the boat = 216 ÷ 12 = 18 km/h So, speed of the boat in still water = {(18 + 12)/2} = 15 km/h So, required time = (180 ÷ 15) = 12 hours
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