Most mathematics students, and surely all mathematicians, are familiar with calculus
optimization problems, in particular, with the problem type in which an open-topped
box is to be made by cutting corners from an a × b sheet of cardboard and folding
up the sides, and students are asked to maximize the attainable volume (see Figure 1).
Let us call this the box problem. Under what conditions is the volume an integer? Or
the dimensions of the wasted cardboard corners? How about the dimensions of the
cardboard?
Interest in such problems is not new: Following Hern and Meel [2], we find the
box problem in an 1852 textbook of Todhunter (see [3] for more about this prolific
author).
Problem 1. [6, Exercise 29, p.193] If a rectangular piece of pasteboard, the sides of
which are a and b, have a square cut out at each corner, find the side of the square that
the remainder may form a box of maximum content.
This article is the result of a coincidence that affirms the problem’s ongoing interest.
Two manuscripts on the box problem were submitted around the same time to The
College Mathematics Journal, one from the quintet Coll, David, Hall, Magnant, and
Wang, and one from Stankewicz. Despite the overlap in content, the authors approach
and generalize the problem in different ways. The editorial board decided to combine
the articles. That work was done by sarah-marie belcastro, Brian Hopkins, and all six
authors.
The authors’ motivations are similar. Coll et al. explain, “In today’s calculus classes
a cry is likely to be heard from the legions of students who are hoping for ‘nice’
solutions to the problems on the next exam. We ask: What can be nicer than integer
solutions?” And Stankewicz says, “As a teacher, I often prefer to assign problems
whose solutions are not just real, but rational. . . For instance, the standard-size sheet
of paper in the United States is 8.5 inches by 11 inches, which does not give a rational
solution. When teaching calculus one summer, I got to thinking about how one might
generate different versions of this problem of the same approximate level, especially
for the creation of multiple versions of tests.”
These questions are of both mathematical and pedagogical interest. Their answers
can be used by faculty across the world, and their solutions are appropriate to present
to future teachers as an application of mathematics to their work.