I like the X9 trick. I'm surprised how many of my adult friends have never seen it. The "tricks" he likes right now are the ones he can understand like n * 1 =

I like the X9 trick. I'm surprised how many of my adult friends have never seen it. The "tricks" he likes right now are the ones he can understand like n * 1 = n for any value of n or n / 1 = n (because you have one circle around everything). I've tried showing him some tricks, but they aren't surprising and cool to him yet.