In several previous posts, I've been calling 6 a magic number in crocheting round objects. It wasn't until this past week that I finally understood where it came from.
I had told him that sc sts are basically square. And, I was telling him that a person was having trouble with a hotpad pattern because of not making the "correct" number of increases per round. He guessed that that number should be 6. I asked him how he knew that, and he replied "simple math". The circumference of a circle increases by 2 π for each increase of 1 in radius -- and 2 π is approximately 6.