<PRE><B>Question 1007208</B>
A man rows a boat 910 feet upstream against a constant current in 14 minutes.
 He then rows 525 feet downstream (with the same current) in 7 minutes.
 Find the speed of the current and the equivalent rate at which he can row in still water.
:
let s = rowing speed in still water in ft/min
let c = rate of the current
then
(s-c) = effective speed upstream
and
(s+c) = effective speed downstream
:
Write a distance equation for each way. Dist = speed * time
:
14(s-c) = 910
 7(s+c) = 525
We can greatly simplify these equations, divide the 1st by 17, the 2nd by 7
then use elimination
s - c = 65
s + c = 75
-------------Addition eliminates c find s
2s = 140
s = 140/2
s = 70 ft/min the speed in still water
:
Find the current using s + c = 75
70 + c = 75
c = 75 - 70
c = 5 ft/min the rate of the current
:
:
Confirm this in the 1st original equation
14(70 - 5) = 910
14(65) = 910


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