The volume of water in a small pool is directly proportional to the depth of water. When there are 10 cubic feet of water in the pool, the depth of the water is 5 inches. How many cubic feet of water are in the pool when the depth of the water is 2 feet?

When two variables are directly proportional, they always make the same fraction. Just make sure you convert 2 feet to 24 inches before you set up your proportion!