<PRE><B>Question 209698</B>
Bill can row 3 mph in still water. It takes him 3 hours 36 minutes to go 3 miles upstream and return. Find the speed of the current. 
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current speed = c
d = rt = 3 miles
t = 3/r
3.6 = 3/(3+c) + 3/(3-c)
3.6(3+c)*(3-c) = 3(3-c) + 3(3+c)
1.2(9 - c^2) = 3-c + 3+c = 6
9 - c^2 = 5
c^2 = 4
c = 2 mph
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It takes 3 hour upstream at 1 mph ground speed, and
0.6 hours downdstream at 5 mph.</PRE>