A boatman goes 2 km against the current of the stream in 1 hour and goes 1 km along with the current in 10 minutes. How long will it take to go 6 km in stationary water?

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Accepted Answer

Step 1: Let the speed of the boat in still water be 'b' km/h and the speed of the stream be 's' km/h.

Step 2: Against the current, the effective speed = (b - s). Given, the boatman covers 2 km in 1 hour against the current.
So, b - s = 2 km/h.

Step 3: Along with the current, the effective speed = (b + s). Given, the boatman covers 1 km in 10 minutes (which is 1/6 hour).
So, b + s = 1 km / (1/6) hour = 6 km/h.

Step 4: Now, we have two equations:
  b - s = 2
  b + s = 6

Adding both equations:
  2b = 8
  b = 4 km/h (speed of boat in still water)

Step 5: Time taken to cover 6 km in still water = Distance / Speed = 6 / 4 = 1.5 hours = 1 hour 30 minutes.

Therefore, the correct answer is 1 hr 30 min.

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