I'm stumped! I'm on this question in my math book that reads something like this: "A gas tank that is 10 meters in length (end to end) consists of a right-cylinder and is capped at either end by a hemisphere. What is the radius of the tank if the volume is 50 cubic meters?" Ok i got as far as 4/3[pi]r^2(r + 15/2) = 50 but I can't seem to figure out how to isolate r. I know I'm overlooking something mundane, but can someone give me a hint? Tanks! Ha ha ha! (get it? Tanks?) Sorry.