## Wednesday, June 7, 2017

### 6/6 Rational Tangles

This Math Club  was a growth exercise for me. I had decided a few week's ago that I wanted to do John Conway's rational tangle game: http://www.geometer.org/mathcircles/tangle.pdf in a future session.  It seemed great for a couple of reasons.

• The problem was posed in a game format that didn't require a lot of supplies.
• The game was physical (Good ones in this class are always hard to find.)
• The connection between the game and rational numbers had a lot of depth.

I also really wanted to stay hands off and maximize the kids own thinking as much as possible. So my challenge to myself was to allow the time for experimentation but keep the kids going all the while sticking to asking questions rather than telling answers.

This is the structure I chose.  First I outlined the rules and had a demo set of kids try out twists and rotates just to make sure everyone understood what we were doing.

For the next 10 minutes or so I had kids in each group create their own tangles and unknot them through experimentation. I mostly observed through this point.  The one exception I made was that its fairly easy to do a twist / rotate / twist combo that gets you back to the starting point. If the kids fell into this path, I'd ask them to add more twists at once i.e. twice 2 or 3 times.

At the end of this phase, I had members from each group make the tangle for the other ones and I asked them to try to make them as challenging as possible.   By this point the kids had developed a reasonable set of strategies that revolved around studying the loops and intuiting the sequence of steps to untangle bit by bit. What was particularly noticeable was they would often rotate through all 4 configurations to find 1 that would improve the tangle if twisted.

Next: I introduced the idea that we were going to map the moves to arithmetic operations. Everyone quickly came up with the idea that twists were  a  +1 operation. Rotations  remained mysterious.  After playing around a few more minutes I added the suggestion that they should try simple configurations and record all the moves they made.

Several ideas developed over the next phase: including are rotate/twists -2? I asked them to try doing 2 twists and seeing if the rotate/twist combo reversed it. (No)  One boy also jumped to the idea of infinity so I was able to ask questions about if we had any states that behaved like infinity i.e. if you twisted them they stayed the same.

Finally, the kids were starting to flag so I intervened  more directly by asking the kids to come up with ideas for what the rotate could mean and had them conduct experiments on simple tangles (usually double twists) to see if they would work. We did this as a group with one of the kids recording the results and tried out 3 or 4 options like multiple by -1.

At this point I was just about out of time so for the last 5 minutes we switched and I  let them do sequences of moves and I would call out the actual state values. Then they were finally able to discover that rotations were a negative reciprocal and that let me do a quick wrap up for the day.

All in all, we worked on the problem for most of the hour and while there were points when the kids were ready to give up, I was able to draw them back into the problem and re-establish flow. Hopefully, I'll have chance to try this again and see if my facilitation can improve further.

#### Further Highlights

In going over the problem of the week: MathForumProblem  a mostly standard linear system story problem with a small twist I had expected a blend of informal and formal solutions.   In past years, I'd get different strategies from bar charts or guess and check all the way to fully symbolic answers. This time around, I had 3 different kids demoing on the whiteboard all using substitution.  I'm impressed how many kids have already made the algebraic transition prior to middle school.

Finally, the most touching moment for me had to do with next week.  I realized after a parent question that a large group of the kids would be absent next Tuesday on a field trip. The excursion is downtown and finishes without transportation back to the school.  This will be our last session for the year and I assumed most of these kids wouldn't be able to attend. I've sent out an email and so far it looks like the parents will arrange carpools to bring the kids back especially to come to Math Club. The fact they were willing to do this makes me feel really happy.