# February, 2013

## Summing a geometric series: Secrets of the Mathematical Ninja

“I don’t know if you were actually working stuff out there, or if you just muttered at random for a bit and guessed,” said the Mathematical Ninja’s cheeky student. Stung, the Mathematical Ninja was forced to explain how he figured out $\left(1 – \frac{1}{8}\right)^{19}$. It’s a simple enough trick that

## Silly Questions Amnesty

It’s 22/2, or – it you’re in the US, 2/22. It’s half-term here in Dorset, which means you’re probably starting to get serious about your revision. (About time, if you ask me!) Drop me a comment below with any burning questions you have!

If you ever bother to run a search for ‘basic maths’ on twitter – something you may not generally do, as you’re probably not the author of a book called ‘Basic Maths For Dummies’ – you’ll find the breakdown of tweets looks something like this: 47%: Teenagers complaining that they

## Squaring biggish numbers, revisited

One of the Mathematical Ninja’s favourite tricks is squaring biggish numbers. He’d secretly like to be Art Benjamin one day. So (inspired partly by Barney), he’s been looking at quick tricks to help him square numbers. He knows the first 25 square numbers by heart (and so should you); he’s

## Silly Questions Amnesty

Look at that calendar flying by! It’s half term next week, already the middle of February – that means only a few more months until those big exams. So what’s on your mind? Any burning questions?

## The 23 problems joke

In my ‘best-selling((Most-given-away would be more accurate)) book n Mathematical Quotations (Where n ~ 100), my favourite joke is: “Maths is a game played according to certain simple rules with meaningless marks on paper.” — David Hilbert (1862-1943), infinite hotelier, mathematical revolutionary, native of Königsberg with 23 problems (but a

## Lives of the Mathematical Ninja: Evariste Galois

Like the most-celebrated rock stars, the most famous mathematicians live fast and die young. Evariste Galois was 20 when he went to meet the Supreme Fascist, on the wrong end of a bullet in a duel. It’s not clear who his opponent was. He’s held up as a romantic hero:

## Silly Questions Amnesty

I’m sure you must have a silly question you’d love to have answered. Something that’s always bothered you. Something you might write in the comments and wait for me to answer.

## Bayes’ Theorem and Minesweeper

I suppose I must have learned about Bayes’ Theorem at sixth form. In those days, maths was Pure and Applied, so I could – and did – largely avoid statistics until midway through my PhD I was roundly mocked by my future boss for not knowing what ‘significant’ meant. I

## Why the Mathematical Ninja hopes for a hard exam

The Mathematical Ninja sighs. “Say that again?” “I hope it’s an easy paper!” says the student, brightly. Wearily, the Mathematical Ninja goes to the board and sketches two curves. They look a little like boa constrictors that have swallowed elephants. “You’re above average, correct?” he asks. The student doesn’t look