Ever since I watched the above clip from Vi Hart I’ve been fascinated with flexagons and so one night this week I made my very own trihexaflexagon. It was after I’d marked a test for one of my classes and even though we’ve spent lessons and lessons on circles there were still some students that got the two formula for area and circumference mixed up so I put the circle formulae on two of the faces. These are strangely satisfying to fiddle with and turn the faces over that I’m hoping they’ll be a nice little revision tool too!
Not sure what a trihexaflexagon is? Well … a flexagon is a flat model usually constructed by folding strips of paper, that can be flexed to reveal faces besides the two on the back and front and by adding the prefix “hexa” to this we have a hexagonal flexagon. What I’ve made however is a “Trihexaflexagon” which is a hexaflexagon with three faces … simples.
You will find the sheet to print your own here -> hexaflexigon 2 and some instructions on how to put it together here -> hexaflexagon instructions
Also worth checking out Hexaflexagons Part 2
Circle formula confusion – my students suffer too!
This helped some of them:
Pi R squarier gives you the area
Two pi R is the perimiTAR
Painful rhyme but they seem to remember it!
i find it easier as a student to remember that the area of a cirlce is pi-r-squared and the perimeter is pie-D
this is because then i am not confused by the 2s and they both have 2 in them.
thanks mel this is great