I think I got the answer but I won't bet the farm on it. First, the Area of a circle is Pi x Radius Squared. This is 3.14 x (.5 x .5) = .785 sq inches. .785 x 120 inches (length) = 94.2 cubic inches. There is 231 cubic inches in 1 gallon, so .785/231 = gallons in 10 feet. This is slightly over .4 gallons in 10 feet.