Yesterday we looked at this interesting geometry puzzle from Catriona Shearer:

My son took a pretty computational approach to the problem and the calculations gave him a little difficulty. Today my main idea was to share Ian Agol’s neat solution, but I wanted to review one piece of yesterday’s calculation with him as an arithmetic review:

Now we moved on to looking at Ian Agol’s solution (using the picture made by Greg Egan):

My son studied this solution and picture for about 10 min before we started the project. Here’s how he explained it:

I liked following up yesterday’s computational solution with this terrific non-computational one.