<PRE><B>Question 476395</B>
A boat travels 30 miles upstream in 5 hours.
 Going downstream, it can travel 60 miles in the same amount of time.
 Find the speed of the current and the speed of the boat in still water.
:
Let c = speed of the current
Let s = speed of the boat in still water
:
Write two distance equations: dist = time * speed
:
5(s - c) = 30
5(s + c) = 60
Simplify, divide both equations by 5, results
s - c = 6
s + c = 12
--------------addition eliminates c, find s
2s = 18
s = {{{18/2}}}
s = 9 mph in still water
then
9 + c = 12
c = 12 - 9
c = 3 mph is the speed of the current
:
:
Check in both equation
5(9 - 3) = 30
5(9 + 3) = 60</PRE>