77. River Crossing Time Calculation A person crosses a river on a paddle boat. He took 4 hours while paddling against the water flow and 3 hours while paddling in the direction of the water flow. On still waters, how long would he take? Added 29 January 2011 Show Solution Solution: Let the speed of the boat in still water be b km/h and the speed of the river current be c km/h. The distance across the river is the same in both cases. When paddling against the current, the effective speed is b - c, and when paddling with the current, it is b + c. The time taken to cross against the current is 4 hours, and with the current is 3 hours. Therefore, we have:Distance = (b - c) * 4 = (b + c) * 3From these equations, we can derive the time taken on still water. Solving these equations gives us the time taken on still water as 3.5 hours.
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