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A boat moves 7kph in still water. It ravels 45 km upriver and 45 km downriver in a total time of 14 hours. What is the speed of the current?
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A boat moves 7kph in still water. It ravels 45 km upriver and 45 km downriver in a total time of 14 hours. What is the speed of the current?
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Question 136970: can you solve?
A boat moves 7kph in still water. It ravels 45 km upriver and 45 km downriver in a total time of 14 hours. What is the speed of the current?
I am more interested in the work than the answer so please show me step by step.
Thanks Answer by checkley77(12844) (Show Source):
You can put this solution on YOUR website! d=rt or d/r=t
45/(7+x)+4/(7-x)=14
[45(7-x)+45(7+x)]/(7+x)(7-x)=14
[315-45x+315+45x]/(49-x^2)=14
630/(49-x^2)=14 now cross multiply
14(49-x^2)=630
686-14x^2=630
-14x^2=630-686
-14x^2=-56
x^2=-56/-14
x^2=4
x=sqrt4
x=2 kmph is the speed of the current.
45/(7+2)+45/(7-2)=14
45/9+45/5=14
5+9=14
14=14
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