SOLUTION: A boat took 2 hours to make a trip down river. The same boat took 10 hours to make the return trip upstream. The river current is moving at a constant rate of 8 miles per hour. Wha

Question 447812: A boat took 2 hours to make a trip down river. The same boat took 10 hours to make the return trip upstream. The river current is moving at a constant rate of 8 miles per hour. What is the average speed of the boat in still water?
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
A boat took 2 hours to make a trip down river.
The same boat took 10 hours to make the return trip upstream.
The river current is moving at a constant rate of 8 miles per hour.
What is the average speed of the boat in still water?
:
Let s = still water speed of the boat
then
(s-8) = effective speed upstream
and
(s+8) = effective speed downstream
;
Write a distance equation, dist = speed * time
:
upstream dist = downstream dist
10(s-8) = 2(s+8)
10s - 80 = 2s + 16
10s - 2s = 16 + 80
8s = 96
s =
s = 12 mph in still water
:
:
Check solution by finding the distances, they should be equal
2(12+8) = 40 mi
10(12-8) = 40 mi
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