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Question 1147728: Adam and Natasha row their canoe 12 miles downstream in 2 hours. After a picnic, they row their canoe back upstream. After 3 hours of rowing, they only travel 12 miles. Assuming that Adam and Natasha canoe at a constant rate, and that the river's current is constant, find the speed at which Adam and Natasha can row in still water.
Answer by ankor@dixie-net.com(22740)   (Show Source):
You can put this solution on YOUR website! Adam and Natasha row their canoe 12 miles downstream in 2 hours.
After a picnic, they row their canoe back upstream.
After 3 hours of rowing, they only travel 12 miles.
Assuming that Adam and Natasha canoe at a constant rate, and that the river's current is constant, find the speed at which Adam and Natasha can row in still water.
:
let s = their speed in still water
let c = the rate of the current
then
(s+c) = their ground speed downstream
and
(s-c) = their ground speed upstream
:
Write a distance equation for each way; dist = time * speed
2(s+c) = 12
3(s-c) = 12
simplify both equations, divide the 1st by 2, the 2nd by 3
s + c = 6
s - c = 4
-------------addition eliminates c, find s
2s + 0 = 10
s = 10/2
s = 5 mph their speed in still water
:
:
see if that checks out (current rate is 1 mph)
2(5+1) = 12
3(5-1) = 12
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