This happened last week but I forgot to write about it. My students and I were practicing the times tables and I showed them the finger trick for multiples of 9. It took a lot of them to understand why I was wiggling my fingers at them, but I happened to be watching one boy when a look of understanding washed over his face and he broke into a huge grin because he realized how cool and useful the trick was. It was one of the best feelings I have ever had.