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Question

A boat covers 4 km upstream and 15 km downstream in 7 hours, while it covers 16 km upstream and 35 km downstream in 23 hours. What is the speed of the current?

The correct answer is

2 km/hr

Let the speed of the boat be B km/hr and the speed of the current be C km/hr. - Upstream speed = (B - C) km/hr and downstream speed = (B + C) km/hr. - From the given data: (4/(B - C)) + (15/(B + C)) = 7 and (16/(B - C)) + (35/(B + C)) = 23. Solving these equations, we find that the speed of the current (C) is 2 km/hr.

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Important Questions from Boat and River

  1. A boat sails 15 km of a river towards upstream in 5 hours. How long (in hours) will it take to cover the same distance downstream, if the speed of river is one-fourth the speed of the boat in still water?

  2. Sudha can travel a certain distance downstream in 6 hours by boat and return to the starting point in 9 hours. If the stream flows at a speed of 3 km/h, how long (in hours) will it take to cover a distance of 67.5 km in still water?

  3. A man covered a distance of 18 km in 3 hours, 7.2 km in 2 hours and 15 km in 5 hours. What is the average distance traveled by him per hour?

  4. A boat covers 20 km upstream and 60 km downstream in 5 hours. Boat covers 30 km upstream and 80 km downstream in 7 hours. What is the speed of boat in still water?

  5. Dalip can row 42 km downstream in 2 hours and the same distance upstream in 2 hours and 48 minutes. How much time will he take to row 31.5 km downstream and 22.5 km upstream?

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