Question
The speed of a boat in still water is 5 times more than
that of the current. If the boat takes 10 hours to cover 200 km upstream, then find the time taken by the boat to cover 420 km downstream.Solution
Let the speed of the current be ‘x’ km/hr
Therefore, speed of the boat in still water = 6x km/hr
According to the question,
6x – x = 200 / 10
Or, 5x = 20
Or, x = 4 km/hr
Required time taken = 420 / (6x + x) = 420 / (7 × 4) = 420/28 = 15 hours
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