Three dimensions
Cones
Area of base = `\pir^2`
Volume of cone = `1/3\times\volume\ of\ a\ cyli\nder`
Volume of cone = `1/3\times \Area\ of\ base\times\ height`
Volume of cone = `1/3\times \pir^2\times\ height`
3 cones fill 1 cylinder (with the same size base and height).
NOTE:
Areas shaded blue are all equal.