SOLUTION: The current in a stream moves at a speed
of 4 mph. A boat travels 5 mi upstream and 13 mi downstream
in a total time of 2 hr. What is the speed of the
boat in still water?
I
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-> SOLUTION: The current in a stream moves at a speed
of 4 mph. A boat travels 5 mi upstream and 13 mi downstream
in a total time of 2 hr. What is the speed of the
boat in still water?
I
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Question 949510: The current in a stream moves at a speed
of 4 mph. A boat travels 5 mi upstream and 13 mi downstream
in a total time of 2 hr. What is the speed of the
boat in still water?
I came up with zero for the speed in still water. Is that correct? Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website! The current in a stream moves at a speed
of 4 mph. A boat travels 5 mi upstream and 13 mi downstream
in a total time of 2 hr. What is the speed of the
boat in still water?
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upstream DATA:
dist = 5 mi ; rate = b-4 mph ; time = d/r = 5/(b-4) hrs
-----
Downstream DATA:
dist = 13 mi ; rate = b+4 mph ; time = d/r = 13/(b+4) hrs
------
Equation:
Total time = 2 hrs.
5/(b-4) + 13/(b+4) = 2
---
5(b+4) + 13(b-4) = 2(b^2-16)
18b - 32 = 2b^2 - 32
-----
18b = 2b^2
------
b^2 - 9b = 0
Factor:
b(b-9) = 0
=-----
Positive solution:
boat speed = 9 mph
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Cheers,
Stan H.
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