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Approximate a ratio by folding a piece of paper

towel-ratio

Warning: you could make a very strong argument I’ve thought far too much about something inconsequential. If that makes your stomach turn, look away now.

This morning in the shower, I had an idle thought about my towel. It was, as always, folded neatly on the toilet seat. A problem that’s been bugging me for a few days is how to pick up the towel by a section of the long edge, so when it unfolds it’s the right way round.

* quiet in the back

The problem is that the short edge and the long edge look the same, and once I’ve folded the towel over a couple of times and had a shower only a madman* would remember which is which. But my towel isn’t square, so it occurred to me that either the longer or the shorter edge, after folding, could be the edge I want. Since I never make a diagonal fold, the long edge is only ever folded on top of the long edge, and likewise for the short edge. I fold the towel until it fits comfortably on top of the toilet seat, and by the time I’ve finished my shower I can’t be relied upon to remember which sequence of folds I did.

Which got me thinking about the ratio between the width and height of my towel: if I know this ratio then, by looking at the towel and counting the number of folds, I can work out which folds I’ve done, and hence which of the sides will unfold to be the long edge.

Maths Object: Correntator

Here’s another one of my favourite maths objects: the Correntator. It’s a simple mechanical tool to add up amounts of money. I bought it for about a tenner (new money) at a market.

This video is extremely shonky. Blame my phone, which can’t bring itself to record for more than 250 seconds at a time.

More information about the Correntator.

I bought isthisprime.com

probable prime

Around about exactly this time a year ago, I bought the frivolous domain name three.onefouronefivenine.com, to celebrate π Day and to indulge my curiosity about a marvellous algorithm to compute π’s digits.

This year, I’ve been thinking about prime numbers, and my hosting provider has run another sale on domain names. So, I’ve bought isthisprime.com. You can probably guess what I’ve made it do.

Maths Objects: polyhedra

Time for some more maths objects! This time I wanted to show you the various polyhedra I’ve got around my desk.