SOLUTION: The speed of a stream is 5 mph. A boat travels 2 miles upstream in the same time it takes to travel 12 miles downstream. What is the speed of the boat in still​ water?
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Question 1055078: The speed of a stream is 5 mph. A boat travels 2 miles upstream in the same time it takes to travel 12 miles downstream. What is the speed of the boat in still water? Found 2 solutions by stanbon, josmiceli:Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website! The speed of a stream is 5 mph. A boat travels 2 miles upstream in the same time it takes to travel 12 miles downstream. What is the speed of the boat in still water?
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Upstream DATA:
distance = 2 miles ; rate = b-5 mph ; time = d/r = 2/(b-5) hrs
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Downstream DATA:
dist = 12 miles ; rate = b+5 mph ; time = 12/(b+5) hrs
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Equation:
2/(b-5) = 12/(b+5)
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2b + 10 = 12b - 60
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10b = 70
boat speed = 7 mph (speed in still water)
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Cheers,
Stan H.
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You can put this solution on YOUR website! Let = the speed of the boat in still water = the speed of the boat going upstream = the speed of the boat going downstream
Let = time in hrs for traveling both upstream and downstream
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equation for going upstream:
(1)
equation for going downstream:
(2)
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(1)
Plug (1) into (2)
(2)
(2)
(2)
(2)
(2)
The speed of the boat is still water is 7 mi/hr
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check:
(1)
(1)
(1)
(1) hr
and
(2)
(2)
(2)
(2) hr
OK
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