# July, 2013

## A reader asks: How does the circle of fifths work?

A fifth - in musical terms - is really three-halves, and if you go through twelve fifths, you end up seven octaves higher. Wait, I'm starting all wrong. A musical note has a frequency - the number of times the sound wave it produces vibrates each second. Middle C, for

## The Tau of SUVAT

The Mathematical Ninja twiddled absent-mindedly with the nunchaku he used as a stress toy. "Do you use SUVAT?" asked the student, timidly. The Mathematical Ninja shrugged. "Yeah, I suppose that's one way." He giggled. "I don't know the SUVAT equations, though... I've been meaning to learn them." "I wouldn't bother,"

## Pascal’s tetrahedron

So, there I was, idly figuring out one of Barney's fiendish puzzles ("How many pairs of dice would you have to throw to be 95% certain of seven being the modal total?") when I started thinking about the binomial expansion (don't tell the Mathematical Ninja!) You know it: if you

## Fibonacci kilometres: how the Mathematical Ninja converts (and how mere mortals can, too)

"You simply multiply by eight-fifths," said the Mathematical Ninja, as if that was the end of it. The student looked hurt. "In my head?" He knew how to multiply by fractions, but much preferred writing things down. Fair enough, I thought. I interrupted, in the way the Mathematical Ninja hates.

## Review: The Noteboard

I LOVE index cards. When I lived in the US, I would routinely make a trip to the bookstore just to pick up more index cards, the better to process my ideas. It's much less intimidating to look at a blank index card than it is to look at a

## Basic maths skills: the ice cream portion

As you might know (if you've spotted the big yellow bar above), I'm training for the Berlin Marathon in memory of my grandmother (you can support me - and the Alzheimer's Society - by sponsoring me here). One of the perks of marathon training is that I get to eat

## How related are Alice and Bob?

The population of Iceland is somewhere around 300,000. It's not an incredibly big island, and there's not a huge amount of immigration and emigration - which means, if you're on the Icelandic dating scene, you have to be fairly careful not to go out with uncomfortably close relatives. Luckily, there's

## Why the binomial expansion is stupid and you shouldn’t use it

The Mathematical Ninja looked offended. For once, it wasn't a student that was the guilty party, it was me. "You're considering a series on the WHAT?!" "The binomial expansion," I said, brightly. "Drivel!" said the Mathematical Ninja "Drivel, piffle and poppycock! Newtonian claptrap, not worth the space made for it

## Wrong, but Useful: Episode 4

In this episode, (who is Dave Gale in real life) and I talk about... Comments on our last episode Weinstein-gate: full coverage via (Peter Rowlett in real life) at the Aperiodical A boy called Tutankhamun: Owen Daniel's TEDx talk, a variation on the Tuesday's Child problem1 Making your cousin cry

## A reader asks: why does $1+1=2$?

A question from my Uncle Bill, who's one of my great heroes and a philosopher of some standing: How does one get from 1 to 2 other than saying by diktat that 2 is the name we give to 1+1? Now, I'm far from the world's greatest expert on the