Making Tetrahedra

I was at the Canberra Maths Association conference a few weeks ago and saw this really simple idea from Maria Quigley from the University of Sydney.

When making models of 3D objects, Maria used those really jumbo sized plastic straws you get at some "bubble tea" outlets. They are useful because you can pass a string through the straw (several times if needed) and tie your shapes together.

So I had a go in my classroom. I bought a few packs of these straws, which are available pretty cheap at some $2 shops. We all sat down and had a go at making a tetrahedron. Here are a few of our results:

Note - collaboration; when we work together we learn so much more. 

They all looked pretty good when I hung them up.

But of course I am an annoying teacher. I wasn't prepared to let it rest at that.

So I started asking some questions.

"What if....?"

"And if we got 2 of them and....?"

"And could you...?"

And suddenly the kids were making some discoveries, like:

"Hey, I can't make this cube stay up."

"Is this a triangular prism?"

"What do you call this shape when you put two tetrahedra together?"

And then they started to construct models of objects I had no idea what to call. 

This is how we learn.