Students will develop a robot that can draw squares with a laser pointer. They will be challenged in relation to their understanding of the relationship between the perimeter and side lengths of a square. In the tasks, students use reasoning to reach possible solutions while simultaneously documenting their work. The lesson can be used in connection with the lesson “Area and squares.”


It is a prerequisite for the lesson that students are familiar with squares, perimeter, and area.


  • Joint module (Fable robot)
  • Laser pointer
  • PC
  • Pen and paper (possibly Geogebra or similar program)

Learning activities

Students work in groups of two. Each group receives a copy of the assignment sheet.

Students develop code for Fable to make the joint module draw a square with a laser pointer. Students document their square by drawing it. To do this, they can use a sheet of a paper as the work surface for the laser pointer. Students mark each corner point (laser dot) and draw the figure by connecting the points with lines. Students will probably realize that they need to include pauses in their code in order to have time to mark the points on the paper.

When students have constructed a square, they are asked in task 1.b. to make Fable construct a new square with a perimeter that is twice the size of the first square they drew. The idea is for students to discover the mathematical relationship between the side length and perimeter of a square – i.e. that when the side length is doubled, the total perimeter also doubles.

If the lesson is carried out together with the lesson “Area and squares,” students can be asked to examine what kinds of relationships they can find in the two assignments.

This could for example be:
If the side length of a square is doubled, the area becomes four times as large and the perimeter becomes twice as long.


Students present their work to another group. In the presentations, students share their results and code.

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