Acyclindrical water tank has a radius of 6 feet and a height of 20 feet. a larger tank with the same height has a volume that is 3 times the volume of the smaller tank. what is the best approximation of the diameter of the larger tank?

since the smaller tank has a volume of 720π, then the larger tank has a volume of 3 times that much or 3*720π, or 2160π, and its height is the same as the smaller one's, 20.

We need to find the volume of the smaller cylinder.  .  For us, that looks like  .  So the volume is .  3 times that is the volume of the larger at .  Using that volume in the formula to solve for the radius we have  .  Divide both sides by 20pi to get  .  Taking the square root of both sides gives us that r = 10.3923  or, in radical form, r = .  Diameter is twice that at 12sqrt(3)