**The Challenge**: Create a Celtic knot, and do some wondering about why you got the number of links that you did. Can you predict how many links you’ll get? (I wrote another blog post on this a while ago, but only go there if you need more examples, because I reveal a lot of the good stuff in it: Knots, Links, & Learning)

*Materials Needed*: Paper, pencil. If you have grid paper, that might help, and here is some special grid paper you can use courtesy of Justin Aion.

Day18 11×15 Celtic Knot Grid

Day18 MAC 16×22 Celtic Knot Grid

(or you can just rotate grid paper 45 degrees like I do in the video below)*Math concepts* *you could explore with this challenge: *arithmetic, combinations & permutations, counting, knot theory, proportions/ratios.