It is probably best to start by making at least one box with squared paper. Younger pupils will probably gain by making more. A display of a series of boxes can be made with the different volumes written in the base.

When a table is made from the different volumes generated by the different sized squares cut from the corners it will indicate where more calculations are required between whole numbers.

A graph shows a very definite maximum.

Continuing with different sized squares, both smaller and larger than 15 cm, will produce some interesting number patterns.