Consider a 1 x 3 grid whose topleft vertex is connected to the bottomright vertex of each of the unit squares. What is the sum of the three acute angles formed by the connecting segments with the unit squares' bases? This is the socalled threesquares problem, often attributed to Gardner. In a recent academic year, the author used a video on this problem, produced by the YouTube channel Numberphile, for a group project in a firstsemester undergraduate module: Mathematical Problem Solving. The project involved collaborative writing on the problem and individual completion of a peerassessment form. We report the outcomes of this project, which give rise to both theoretical and pedagogical discussions. The theoretical discussion comprises seven alternative solutions to the problem, as well as a generalisation to the case of identical parallelograms forming an arbitrarysized grid whose topleft vertex is connected to the bottomright vertex of each parallelogram. The pedagogical discussion highlights the peerassessment form's effectiveness in detecting unequal group members' contribution, as well as the students' inadequate communication skills. The latter, which has consistently raised concerns, subsequently led to the module being developed and renamed as Mathematical Writing and Reasoning, whose realisation commenced the following academic year.
