Mathematical problem: what is the minimum material used to build a cylindrical container (without cover) with a volume of V when the bottom radius and height are respectively?
When the cylindrical surface is unfolded into a square, the least material is saved.
So 2πr=h
Because V=πr again? h=πr？ (2πr)=2π？ r？
So r? =V/2π？ )
r=？ √(V/2π？ )
h=2π*？ √(V/2π？ ))