A boat which has a speed of 5 km/hr in still water crosses

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A boat which has a speed of 5 km/hr in still water crosses a river of width 1 km along the shortest possible path in 15 minutes. The velocity of the river water in km/hr is

1. 3
2. 4
3. √21
4. 1

Correct Option: A

Speed along the shortest path

	1	= 4 km / hr
	15 / 60

Speed of water v = √5² - 4² = 3 km / hr