Question
When travelling with the current, a man takes 5 hours
to cover the distance that he would've covered in 15 hours while travelling against the current. If the current flows at 8 km/h, then find the time taken by the boat to cover 24 km in still water.Solution
Let the speed of the boat in still water be 'x' km/hr Therefore, distance covered in upstream = 15 X (x - 8) km Also, distance covered in downstream = 5 X (x + 8) km According to the question, 15 X (x - 8) = 5 X (x + 8) Or, {(x + 8)/(x - 8)} = (15/5) = (3/1) Or, x + 8 = 3x - 24 Or, 2x = 32 => 'x' = 16 So, speed of the boat in still water = 16 km/h So, required time = (24/16) X 60 = 90 minutes
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