Growing up, my favourite number was 4, so I especially loved pulling together number 004 for you this week!

I first gained an insight into prime numbers upon realising that you could split 4 into two groups of 2, as opposed to the numbers 5 or 7 or 11 which couldn’t be broken into equal parts.

Similarly, doubling 2 gives 4, and doubling 4 gives 8, followed by 16, 32, 64, 128 … Realising this could go on forever revealed to me that the counting numbers must be infinite. Thanks 4 - you still rock! Check out my 4 facts about 4 further below.

## No problemo

You may have seen me recently on social media promoting the online maths hub Problemo. The Australian Mathematics Trust has taken questions from 40 years of the Australian Mathematics Competition and compiled them on the Problemo website. Using its simple chilli rating system 🌶️🌶️🌶️ teachers can quickly find activities at the right difficulty level for any student, build quizzes to test and challenge them, and generate resources to share on the big screen, print or distribute to devices. Teachers can apply for an account and trial Problemo for free to see how it works. If you think your child’s teacher would be keen, send them to problemo.edu.au. Down the track, this great resource will be available for parents too. Watch a quick video explaining the site

## Enjoy these fascinating numerical facts about 4!

First composite number Having counted past the prime numbers 2 and 3, we get to 4 which is the first 'composite' number. In fancypants maths speak, writing 4 = 2x2 'decomposes 4 into its prime factors'.

Counting letters Four is the only number that when spelled out contains its own amount of letters. Cool hey? Can you work out which number is the only one whose letters are spelled out in alphabetical order?*

Unlucky in China In Chinese culture the number '4' is considered unlucky, because the word for '4' sounds very similar to the word for death. Many casinos do not have a 4th or 14th floor so as not to deter Chinese gamblers.

Four Colour Theorem The famous Four Colour Theorem states that no more than 4 colours are needed to colour all the regions of any map, so that no two neighbouring regions are the same colour. **

* 40. The word 'forty' begins with an 'f' and proceeds alphabetically through 'o', to 'r', 't' and 'y'. It is the only number that spells out alphabetically! ** The Four Colour Theorem was proven in 1976 by Kenneth Appel and Wolfgang Haken. It was the first major mathematical theorem to be proven using a computer which at the time was very controversial. Computers are now regularly used in mathematical discoveries.

## INSPIRATIONAL THINKERS & DOERS - Prof. Geordie Williamson,

## On AI and being wrong 99% of the time

Artificial Intelligence (AI) already impacts our lives in so many ways. Targeted ads hit us in the metaverse, Tesla’s safety statistics continue to improve, and who would have known I’d fall in love with the Netflix documentary Cheer? The Netflix AI of course (#TeamNavarro). Recently at the University of Sydney’s public talks program, I chatted with one of the world’s leading mathematicians about AI. Prof. Geordie Williamson shared the fascinating insights a neural network gave him about a thorny geometric problem that he had danced with for over a decade. Most stunningly, the AI didn’t just crunch out billions of calculations, or use brute force to do what humans could have otherwise done just more quickly. Instead, the AI focused him on a section of the geometry previously unconsidered. The final formula? “A bit the humans came up with” and “a section for which the AI can take credit”. While he’s confident he won’t be out of a job for a while, Prof. Williamson says this sort of interaction was very much in the vicinity of “computational intelligence”. Or as I put it to him - given that working at the cutting edge of knowledge sees you being wrong “99% of the time”, if AI could reduce that to even 97% it would effectively mean we could triple the number of awesome Geordie Williamsons we already have. You can catch his fascinating talk and our Q&A session in video or podcast form here Yours in numbers, Adam

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