<p>What is the largest-volume rectangular cuboid (henceforth, called a block in this article) that can be completely wrapped with a given rectangular sheet of paper, whose one edge must align with an edge of the cube, without cutting the paper and without leaving any part of the block visible?</p><p>On the one hand, to make the solution intelligible to younger students, we solve the problem without using calculus. On the other hand, to motivate them to learn calculus, we exhibit how much easier the solution is if one knows calculus.</p>