A canoeist paddled down a river a distance of 2 miles in 45 minutes. Paddling up-stream on his return, it took him 90 minutes. Find the rate of the canoe in still water.

Speed of canoe in still water we will denote it CS and water itself has a speed we denote it WS. Downstream will be (CS + WS)*45 = 2, Upstream will be (CS - WS)*90 = 2. Solve the system you will find canoe speed in still water and the water speed as well. 90CS = 90WS +2, CS = WS+ 1/45 put it in the first function 90WS +1 = 2, WS = 1/90 miles per minute, CS =1/30 miles per minute.

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