SOLUTION: A boat went 8 kilometers upstream and returned all in 2 hours. If the current was running at 3km/hr, what is the boat’s speed in still water?
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-> SOLUTION: A boat went 8 kilometers upstream and returned all in 2 hours. If the current was running at 3km/hr, what is the boat’s speed in still water?
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Question 1129775: A boat went 8 kilometers upstream and returned all in 2 hours. If the current was running at 3km/hr, what is the boat’s speed in still water? Answer by ikleyn(52932) (Show Source):
Let x be the boat speed in still water, in km/h.
Then your "time" equation is
+ = 2 hours.
8*(x+3) + 8*(x-3) = 2*(x+3)*(x-3)
8x + 24 + 8x - 24 = 2*(x^2-9)
16x = 2x^2 - 18
2x^2 - 16x - 18 = 0
x^2 - 8x - 9 = 0
= = = .
Only positive root x = = 9 km/h is meaningful.
Check. + = = = = 2 hours. ! Correct !
Answer. The speed of the boat in still water is 9 km/h.
Solved.
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It is a typical and standard Upstream and Downstream round trip word problem.
