Question

When travelling with the current, a man takes 6 hours to cover a certain distance that he would've covered in 10 hours while travelling against the current. If the current flows at 4 km/h, then find the distance (one way) covered by the boat.

A 120 km Correct Answer Incorrect Answer
B 110 km Correct Answer Incorrect Answer
C 100 km Correct Answer Incorrect Answer
D 80 km Correct Answer Incorrect Answer
E 96 km Correct Answer Incorrect Answer

Solution

Let the speed of the boat in still water be 'x' km/hr Therefore, distance covered in upstream = 10 X (x - 4) km Also, distance covered in downstream = 6 X (x + 4) km According to the question, 10 X (x - 4) = 6 X (x + 4) Or, {(x + 4)/(x - 4)} = (10/6) = (5/3) Or, 3x + 12 = 5x - 20 Or, 2x = 32 => 'x' = 16 So, speed of the boat in still water = 16 km/h So, required distance = 6 X (16 + 4) = 120 km

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