Volume of cylinder = π.R².h , where R = radius and h = height
Let's replace h by 2h:
V₁= πR².(2h) → V₁ = 2π.R².h
Now let's double R, the radius (and keep h as h)
V₂ = π.(2R)².h → V₂ = 4.π.R².h
Compare V₁ to V₂→ (V₁ = 2π.R².h and V₂ = 4.π.R².h).
It's obvious that V₂ = 2.V₁
