Question 979731
A jet boat is used to take canoers 200 miles upriver to their starting point.
 As the driver of the jet boat, Jeremy knows that it will take him 5 hours to get the canoers upstream, but only 4 hours to get the boat back downstream after dropping the canoers off, as long as he keeps the boat moving at a constant speed. 
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So what is the question? You just made a couple statements.
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It is possible to find the jet ski speed in still water and the speed of the current
let s = the speed of the jet ski in still water
let c = the rate of the current
then
(s-c) = effective speed upstream
nad
(s+c) = effective speed down stream
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leave it to lyou to find the rate of the current
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Write a distance equation for each way. dist = speed * time
5(s-c) = 200
4(s+c) = 200
simplify both equation, divide the 1st by 5, the 2nd by 4 and you have
s - c = 40
s + c = 50
----------Addition eliminates c, find s
2s = 90
s = 90/2
s = 45 mph is the speed of the jet ski in still water