Question
The speed of the boat in still water is 9 km/hr and the
speed of the stream is 6 km/hr. A boat goes 90 km downstream with its usual speed but at the time of returning the speed of the boat in still water is doubled. Find the total time taken by boat to cover the whole distance.Solution
According to the question, Required time = 90/(9 + 6) + 90/(18 – 6) => 90/15 + 90/12 => 6 + 7.5 = 13.5 hours
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