Given a unit square of paper, you are to create a box from it with the largest volume.
Letting the new height be "x", the sides of the box becomes (1-2x).
(By cutting away squares at the corners with sides "x")
Thus, the volume of the box, as a function of "x" becomes V(x)=(1-2x)^2*x.
We will find the extrema of the volume by differentiating the volume function, and determining the values of "x" giving V'(x)=0.
We get: V'(x)=(1-2x)^2-4x(1-2x)=(1-2x)*(1-6x).
Thus, maximum volume occurs for x=1/6, giving maximum volume V(1/6)=2/27