SOLUTION: Jeremiah can kayak downstream a distance of 21 kilometers in 3 hours. Going upstream, he can kayak a distance of only 24 kilometers in 4 hours. How fast could Jeremiah kayak in sti

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Question 662501: Jeremiah can kayak downstream a distance of 21 kilometers in 3 hours. Going upstream, he can kayak a distance of only 24 kilometers in 4 hours. How fast could Jeremiah kayak in still water (if there were no current)?
Found 2 solutions by stanbon, Alan3354:
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
Jeremiah can kayak downstream a distance of 21 kilometers in 3 hours. Going upstream, he can kayak a distance of only 24 kilometers in 4 hours. How fast could Jeremiah kayak in still water (if there were no current)?
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Downstream rate: dist/time = 21/3 = 8 km/hr
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Upstream rate: dist/time = 24/4 = 6 km/hr
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Equations
downstream Eq: b + c = 8 km/hr
upstream Eq::: b - c = 6 km/hr
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Add and solve for "b":
2b = 14 km/hr
boat speed = 7 km/hr
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Solve for "c":
b + c = 8
7 + c = 8
current = 1 km/hr
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Cheers,
Stan H.
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Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
Jeremiah can kayak downstream a distance of 21 kilometers in 3 hours. Going upstream, he can kayak a distance of only 24 kilometers in 4 hours. How fast could Jeremiah kayak in still water (if there were no current)?
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d'stream speed = 21/3 = 7 km/hr
u'stream = 24/4 = 6 km/hr
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His speed is the average = 6.5 km/hr