Logical Psychology

I posed my son a puzzle today. He’s a student, in senior high school, and exams are ever in his mind. I told him a story of four students who missed their exam, and gave him some information about them.

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How To Vote Mathematically!

[This is a back issue of one of this site’s newsletters]

About half of you reading this are from the United States. At least, that’s my guess, based on my website‘s traffic statistics.

About a quarter – half of that half – will be voting in the coming Presidential Election, or have already done so. At least, that’s my guess, based on turnout stats I skim-read on Wikipedia.

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Magic Squares from Latin Squares

The most recent game I uploaded to this site is a Printable Latin Square Puzzle. The goal of the puzzle is to arrange a set of 16 cards into a 4 by 4 grid, following certain rules.

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The Puzzle Universe – A History of Mathematics in 315 Puzzles

The other day I received a marvellous package in the post. Inside was a book, The Puzzle Universe, by Ivan Moscovich, published by Firefly Books. Ivan Moscovich has made a career out of making amazing mathematical puzzles and games.

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More Infinite Number Weirdness

Some time back, I had a bad habit. I would open a cupboard to get something, then forget to close it. My wife was somewhat miffed by this – understandably, because our kitchen had an infestation of moths at the time. So, she found herself having to tell me, again and again – close the cupboard doors!

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Deconstructing April Fool’s Day

Okay, I admit it – my previous blog post was published on April 1. The foundations of mathematics are not really under attack, not now. But they were once!

Here’s a famous puzzle: imagine a village barber, who cuts the hair of everyone who doesn’t cut their own hair. Sounds simple enough, but who cuts the barber’s hair?

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Arithmetic Of The Infinite

Infinite numbers are weird. They gnash their teeth against our intuition. They don’t behave how, deep down, we think numbers ought to behave.

That should not be surprising, since our intuition was formed around tiny little numbers like 3.1, 4000 or seven billion and two.

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What Is Counting?

My son asked me a riddle this afternoon – “What goes up but never down?”

I said “An elevator!”

He seemed surprised by my answer, so I said “Voyager I!”

Then he complained that the riddle was so generic, there were millions of possible answers. I asked him if there was some traditional answer I was supposed to give, and he said that he didn’t know of one.

Do you?

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Circles wherever you look.

You see a silhouette of a three-dimensional shape. The silhouette is a circle. Then, you turn to get another view. The new silhouette is still a circle, so you turn again. And again. Every time you look at the shape, you see a circular outline.

Is it a sphere?

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