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Since the distance downstream (with the current) equals the distance upstream (against the current), and if we: Let B stand for the speed (rate in mph) of the boat in still water, and using the formula rate X time = distance, the equation will be: (B+7) x 3 = (B-7) x 5 3B + 21 = 5B - 35 56 = 2B B = 28 mph

Traveling downstream, the current will cause the boat to go faster so the 7 mph current is added to the boat's still water speed. Traveling upsteam the current slows or decreases the boat's rate so the current's speed is subtracted from the boat's still water speed.

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Q: It takes a motor boat 3 hours to make a downstream trip with a current of 7 miles per hour the return trip against the same current took 5 hours find the speed of the boat in still water?
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