Rate of travel word problem.?

couple guys in a canoe
4 hours to travel 24 miles downstream
6 hours to travel 18 miles upstream
What is the rate of the current?
What is the average speed in still water?

Go to youtube and there is a professor who puts his calculus lessons on the internet, check it out

downstream speed = still-water speed + current
upstream speed = still-water speed - current
downstream + upstream = 2(still-water speed)

downstream speed = 24 mi/4 hr = 6 mi/hr
upstream speed = 18 mi/6 hr = 3 mi/hr
downstream + upstream = 9 mi/hr = 2*(still-water speed)
still-water speed = 4.5 mi/hr
current = 6-4.5 = 1.5 mi/hr

Let x = speed of current
speed of canoe downstream is 24miles/4hr. or 6 miles/hr.
speed of canoe upstream is 18miles/6 hr. or 3 miles/hr.
Assume the canoe travels at the same speed both ways;
so
average speed of canoe in still water = s
s + x = 6mile/hr
s - x = 3mile/hr
Add equations
2s = 9 miles/hr
s= 4 1/2 miles/hr speed in still water
x = 6 - 4 1/2 = 1 1/2 miles/hr. rate of current

http://www.worldtravelandtourism.net/mavericktravelbrisbane/milestravel.html