SOLUTION: The speed of a boat in still water is 20 mph. If the boat travels 120 miles downstream in the same time that it takes to travel 70 miles upstream, find the speed of the current.

Question 931721: The speed of a boat in still water is 20 mph. If the boat travels 120 miles downstream in the same time that it takes to travel 70 miles upstream, find the speed of the current.
Answer by TimothyLamb(4379) (Show Source): You can put this solution on YOUR website!
x = speed of current
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s = d/t
t = d/s
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downstream:
t = 120/(20 + x)
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upstream:
t = 70/(20 - x)
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equate times:
120/(20 + x) = 70/(20 - x)
120(20 - x) = 70(20 + x)
2400 - 120x = 1400 + 70x
190x = 1000
x = 1000/190
x = 5.263157894740000
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answer:
x = speed of current = 5.26 mph
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