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1). 12.5 km/hr2). 12.1 km/hr3). 12.4 km/hr4). 12.8 km/hr |
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Answer» Let speed of boat in still water is SB, speed of stream is SC, and Speed of boat in downstream is SD Speed of boat in downstream, SD = SB + SC = 8 + 2 = 10 km/hr Average Speed of the boat $(= \frac{{40\; + \;36\; + \;45}}{{\frac{{40}}{{10}}\; + \;\frac{{36}}{{10\; + \;2}}\; + \;\frac{{45}}{{12\; + \;3}}}} = \frac{{121}}{{4\; + \;3\; + \;3}} = \frac{{121}}{{10}})$ ∴ Average Speed of the boat = 12.1 km/hr |
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