## Archive for Math

### How not to describe the Cantor set

The latest book from my unread-books shelf is Fractals, Chaos, Power Laws, by Manfred Schroeder, which I am currently perusing over lunch. It belonged to my father, so it’s been sitting on my shelf waiting for me to read it for 15+ years. I already knew that it had pretty fractal pictures in it, and […]

### Checking the math

When I see numbers in fiction that are in some kind of mathematical relationship with each other, I reflexively check the math. (Well, for basic math/arithmetic, anyway.) Like, if a story says “They traveled at 500 mph from California to Japan, arriving in 45 minutes,” then I think, Hmm, it’s 5,000+ miles from California to […]

### What does 95% vaccine efficacy mean?

I’ve seen several web pages that explain how to calculate vaccine efficacy, but most of them explain it in terms of a formula rather than explaining what the formula means. Here’s the simplest conceptual explanation I’ve seen: a VE of 90% indicates […] a 90% reduction from the number of cases you would expect if […]

### 10…08 is divisible by 18

I recently had occasion to learn that 108 and 1008 are both divisible by 18. Which led me to wonder whether any integer consisting of 1 followed by some number of 0s followed by 8 is divisible by 18. And in fact it turns out to be, and I came up with two fun proofs […]

### Kosticks

Yesterday, I met Jane and John Kostick, the creators of many delightful and amazing and lovely 3D-geometrical art puzzles and structures, mostly in wood and metal. Their website shows a bunch of their work. Their YouTube channel shows videos of the construction and/or use of various pieces. And their Facebook page provides some more photos […]

### February has 8! minutes

It turns out that there are 8 factorial minutes in February. And that’s not just a random coincidence; in fact, you can demonstrate that it’s true without performing any multiplication at all, just some easy factoring. February contains four weeks. The number of minutes in four weeks can be expressed as: 4 weeks x 7 […]