Perimeter

The numbers in the regions of the figure at the right indicate the perimeter of each region.

Note that the diagram is not to scale.

How long is the outer (red) boundary of the region?

This is a grade 9 problem that develops reasoning, pattern-recognition, group-work and, if you wish, writing.

We like this problem because it is simple and compelling and it’s really about structure. Another reason is that while the solution is simple enough, there are different ways to present it and that makes presentation an interesting task to give the student.