### Review: Snowflake Seashell Star, by Alex Bellos & Edmund Harriss

Snowflake Seashell Star is a new mathematical colouring book, by Alex Bellos and Edmund Harriss, aimed at the lucrative ‘grown-up colouring books’ market that’s sprung up recently, heavily intersected with people who are interested in maths – the book can be used as a regular colouring book, but contains lots of interesting mathematical things, and mathematicians will love it. I wouldn’t have expected anything less from maths adventurer Bellos and mathematical artist and tiling fan Harriss, whose personalities both come through in the book – from the beautiful illustration to the playful style (and there’s a sneaky Harriss Spiral in there too).

The first thing I did in order to properly review the book was check an important mathematical fact, in case anyone was worried. And yes, everything in it is colourable using four colours or fewer. Phew.

### New York Times puzzle is pure game theory

The Upshot is a column in the New York Times based around analytics, data and graphics. (It was conceived around the time when Nate Silver left to work for ESPN). Earlier this week, managing editor David Leonhardt and data journalist Kevin Quealy posted an interesting puzzle, entitled ‘Are You Smarter Than 49,485 other New York Times Readers?’

The puzzle consists of a simple question – you need to pick a number between 0 and 100, and all 49,485 of the responses will be collated (assuming that every single one of the Times’ readership actually enters a number) and averaged. If your guess turns out to be the closest whole number to two-thirds of the average guess, you are clever and you win.

### New pentagonal tiling discovered

If you’re into tilings, or just looking to redo your bathroom in the most modern way possible, there’s big news. A team of researchers at the University of Washington-Bothell have discovered a previously unknown way to tile a plane using irregular pentagons.

### Review: Cakes, Custard and Category Theory by Eugenia Cheng

We’ve often mentioned category theorist and occasional media-equation-provider Eugenia Cheng on the site, and she’s now produced a book, Cakes, Custard and Category Theory, which we thought we’d review. In a stupid way.

### UK National Lottery: now 21% more balls (rounded up)

This week, it was announced that from October the UK’s National Lottery, currently operated by Camelot and already providing a veritable Merlin’s cave of probability lessons for maths teachers, will be changing the rules for its main ‘Lotto’ draw. The main changes are that a new £1m prize will be added to the raffle element you didn’t know already happens, and that matching two balls will win a free ‘lucky dip’ ticket in the subsequent draw. The fixed £25 prize for matching three balls remains on the round table (even though it sometimes causes hilarious number gaffes).

But the Sword of Damocles hanging over Camelot’s changes is that there will be an extra ten balls to choose six from (59 instead of 49), dramatically lengthening the odds of winning all of the pre-existing prizes. This is our round-up of the media’s coverage of this mathematical “news”.

### π and constrained writing

It’s a tool; a ratio, providing us simple rules for doing circular estimates. Admired regularly – and we all remember that today’s pi! Hooray! Let’s eat pie.

You may have noticed that the first paragraph of this article was immensely poorly written, and didn’t sound like good writing at all. And you’d be right – except writing it wasn’t easy as you’d think. I’ve written it under a constraint – that is, I’ve picked an arbitrary rule to follow, and have had to choose my words carefully in order to do so.

### π and the Mysterious Excel Function

Users of Microsoft’s flagship 2D-array-based data-organisation tool Excel will be aware of some if its more recondite functions. From the occasionally useful

RIGHT: returns the substring of a given length from the right-hand end of a cell’s contents

to the wilfully obscure

TBILLPRICE: gives “the price per \$100 face value for a Treasury bill” when supplied with its settlement date, maturity date and discount rate

to the downright cryptic

N: obviously, converts its argument to a numeric format if it can

along with approximately 340 others, Excel’s abilities are near limitless.

But one function seems singular in the sheer decadence of its inclusion.