# Crossnumber winners, issue 09

With issue 10 of Chalkdust fast approaching, it’s time to announce the winners of the Chalkdust prize crossnumber #9! Before we reveal the winners, here is the solution of the crossnumber.

 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 9 6 4 8 8 9 3 9 4 6 6 1 6 9 4 1 3 1 1 1 7 2 5 9 5 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 9 2 2 8 2 0 8 7 9 1 9 2 2 2 9 2 3 5 8 3 8 3 6 1 5 3 3 7 1 9 9 5 7 1 2 2 9 1 9 2 2 2 9 2 8 1 6 3 4 2 1 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 8 9 9 4 7 4 3 2 7 4 2 3 4 0 7 4 1 2 3 6 6 4 8 3 3 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9

The sum of the across clues was 2222222406182591.

There were 100 entries, 66 of which were correct. The randomly selected winners are:

1. Matt Hutton, who wins a £100 Maths Gear goody bag,
2. George Lambert, who wins a Chalkdust T-shirt,
3. Sami Wannell, who wins a Chalkdust T-shirt,
4. Deborah Tayler, who wins a Chalkdust T-shirt.

Well done to Matt, George, Sami and Deborah, and thanks to everyone else who attempted the crossnumber. See you shortly in issue 10…

# Prize crossnumber, Issue 09

Our original prize crossnumber is featured on pages 54 and 55 of Issue 09.

### Rules

• Although many of the clues have multiple answers, there is only one solution to the completed crossnumber. As usual, no numbers begin with 0. Use of Python, OEIS, Wikipedia, etc. is advised for some of the clues.
• One randomly selected correct answer will win a £100 Maths Gear goody bag, including non-transitive dice, a Festival of the Spoken Nerd DVD, and much, much more. Three randomly selected runners up will win a Chalkdust T-shirt. Maths Gear is a website that sells nerdy things worldwide, with free UK shipping.
• To enter, enter the sum of the across clues below by 9 September 2019. Only one entry per person will be accepted. Winners will be notified by email and announced on our blog by 28 September 2019.

# Dear Dirichlet, Issue 09

Moonlighting agony uncle Professor Dirichlet answers your personal problems. Want the prof’s help? Send your problems to deardirichlet@chalkdustmagazine.com.

### Dear Dirichlet,

My husband and I have found ourselves in a long-distance relationship. His company offered him a large promotion if he moved to Canada for six months, but it seems now that the position will require more time. I’m not sure that I want to move out there with him, or that I could be happy knowing he had to move back here. Conversation with the time difference is hard as well. Any tips?

— Getting tensor, Four Oaks

# Horoscope, Issue 09

Aries
Mar 21 – Apr 19

Your research output doesn’t look so bright until a tall, dark, handsome stranger presents you with a proof of the Riemann hypothesis.
Torus
Apr 20 – May 20

The heavens are not in your favour, and people may try to take advantage of you. Don’t let them take you for a mug.
Gemini
May 21 – Jun 20

Tomorrow you will wake up in a parallel universe which is identical to this one, except for the fact that no one ever invented the Banach–Tarski paradox. So you get to invent it! Good for you!

# Top Ten: Chalkdust regulars

This issue, Top Ten features the top ten Chalkdust regulars! Then vote here on the top ten issues of Chalkdust for issue 10!

At 10, it’s the page you probably didn’t use to find this page: the contents page.
At 9, it’s the big block of text on the page that no-one looks at: the editorial.
Did you know that the online vote is the reason that did you know made it to number 8?
At 7, but about to move to 14 as an infinite number of people have arrived, it’s Hilbert’s hotel: the game.
At 6, it’s the puzzles page. Can you work out why it’s so popular?
At 5, and causing a moderate amount of recursion, it’s top ten.
At 4, despite being deemed not hot, it’s what’s hot and what’s not.
Storming back into the top ten after not being seen since issue 03, it’s the horoscope.

### Dear Dirichlet,

what is the second most popular Chalkdust regular?

Dirichlet says: No idea.

Topping the pops this issue, it’s the crossnumber.

# On the cover: Harriss spiral

The golden ratio (1.6180339…) has a rather overblown reputation as a mathematical path to aesthetic beauty. It is often claimed that this number is a magic constant hidden in everything from flowers to human faces. In truth, this is an exaggeration, but the number does however have some beautiful properties.

The golden ratio, often written $\phi$, is equal to $(1+\sqrt5)/2$, and is one of the solutions of the equation $x^2=x+1$. The other solution of the equation is $(1-\sqrt5)/2$, or $-1/\phi$. One of the nicest properties of the golden ratio is self-similarity: if a square is removed from a golden rectangle (a rectangle with side lengths in the golden ratio), then the remaining rectangle will also be golden. By repeatedly drawing these squares on the remaining rectangle, we can draw a golden spiral. Continue reading

# What’s hot and what’s not, Issue 09

Maths is a fickle world. Stay à la mode with our guide to the latest trends.

### HOT The 10-issue challenge

We challenge you to write an article for issue 10 of Chalkdust.

### NOT The 10-year challenge

What’s so special about base 10 anyway?

# Top ten vote issue 09

What is the best issue of Chalkdust?

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