SOLUTION: A boat can go 20 km downstream in 2 hours. The return trip takes 5 hours. What would the speed of the boat be if there was no current? What is the speed of the current?
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Question 515488: A boat can go 20 km downstream in 2 hours. The return trip takes 5 hours. What would the speed of the boat be if there was no current? What is the speed of the current? Answer by oberobic(2304) (Show Source):
You can put this solution on YOUR website! d = r*t is the basic distance equation.
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d = 20km
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s = speed of the boat in calm water
c = speed of the current
so
r = s-c going upstream (against the current)
r = s+c going down stream (with the current)
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Going downstream...
d/r = 2 hr
d/(s+c) = 2
20 = 2(s+c)
2(s+c) = 20
s+c = 10
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Going upstream
d/r = 5 hr
d/(s-c) = 5
20 = 5(s-c)
5(s-c) = 20
s-c = 4
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s + c = 10
s - c = 4
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2s = 14
s = 7 km/h
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c = 10-s
c = 3 km/h
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Check the distances
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2 * (7+3) = 20 km
5 * (7-3) = 20 km
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Answer: The boat can achieve 7 km/h in still water; the current is 3 km/h.
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Done.
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