Kyle D. Evans - Maths tricks to blow your mind : a journey through viral maths

For Edwin and Juno, and all the emergency homeschooling parents.

First published in the United Kingdom in 2021 by Allen & Unwin, an imprint of Atlantic Books Ltd.

Copyright Kyle D. Evans, 2021

The moral right of Kyle D. Evans to be identified as the author of this work has been asserted by him in accordance with the Copyright, Designs and Patents Act of 1988.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior permission of both the copyright owner and the above publisher of this book.

Every effort has been made to trace or contact all copyright holders. The publishers will be pleased to make good any omissions or rectify any mistakes brought to their attention at the earliest opportunity.

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A CIP catalogue record for this book is available from the British Library.

Hardback ISBN: 978 1 83895 366 9
E-book ISBN: 978 1 83895 367 6

Printed in Great Britain

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My smartphone lights up with the familiar red blob: I have a Facebook notification. I can see that its from an old school friend I havent seen for 20 years; theyre probably just inviting all their contacts to like their new business venture. Or, even worse, they could have found an old photo from the class of 2000, when my nickname was Spud because my head looked like a potato. Im definitely going to ignore it.

But whats the worst that could happen? Hey, Im a sucker for that dopamine hit, and, besides, Im just sitting here doing nothing while my kids watch Moana for the third time today. What the hell, Ill have a look:

Maths trick: A% of B = B% of A.
So 8% of 25 is equal to 25% of 8.
25% of 8 = 2.

Spud! Youre into maths right? How did I never know this?!

Yes, I suppose it would be fair to say that Im into maths, spending most of my working life teaching maths in a sixth-form college, then on weekends changing costume in a phone booth to perform live maths shows for children and adults. Yet the number of people I have ever taught or performed to pales in comparison to the number of people who engage with viral social media maths puzzles and life hacks like the above.

It is quite amazing, isnt it? Did you know that 8% of 25 is the same as 25% of 8? I think of this as a wonderful example of the good side of viral maths: something that everyone whos been through school can relate to, and is obvious once youve seen it, but the majority of people seem to go through their entire education without knowing about. What better use of social media? Raising the mathematical literacy of millions of people who could be cynical about that?

On the other hand, we have the dark side of viral maths: the provocative, binary choice strand of social media problems that are designed to provoke polarization and division (not that type):

Lets see whos dumb.

60 + 60 0 + 1 = ?

This type of problem seems to be the most popular of all viral maths questions, probably because it is intentionally divisive. If weve learnt anything since the invention of the internet, its that people just cant resist (virtually) screaming at any old stranger on the other side of the world who is naive enough to think that the answer is 1 when its obviously 61!

Either way, Im fascinated by what makes things go viral, and being a jack of all mathematical trades Im especially interested in why certain maths problems take off while others flounder.

I feel its important to mention up front that this is a book entirely about viral social media maths, and absolutely in no way about the mathematics of virus transmission. There are many great books about that particular topic and I am barely fit to lace the boots of the good people working in this area. What exactly do we mean when we say something has gone viral though? When did the language of viruses and epidemics start being used to describe popular videos, graphics or even just ideas?

Richard Dawkins is the godfather of the word meme, first using it in his 1976 bestseller The Selfish Gene, meaning an idea, behaviour or style that spreads from person to person within a culture. But the online etymology dictionary actually dates the use of viral outside of medicine even earlier, with Jeffrey Rayport of Harvard Business School first using the term viral marketing in 1972. Scratch a little deeper (on Wikipedia) and youll find the philosopher Marshall McLuhan describing technology as being virulent in nature as far back as 1964. But despite this there can be no doubt that viral has only really taken off as a term separate from actual diseases since the age of social media.

Interestingly, when I asked friends and family across various generations to name what they thought of as the all-time epitome of a viral video, tweet, image or meme, the most popular response to come back was the Ellen Oscars selfie. This was a photograph taken by the television presenter Ellen DeGeneres at the 2014 Oscars, featuring A-listers such as Brad Pitt, Julia Roberts, Meryl Streep, Lupita Nyongo and, fantastically, Lupitas opportunistic non-acting plus-one, her brother Peter. This image was for some time the most retweeted post in Twitter history, though it has since been surpassed by four tweets: two by Japanese billionaire Yusaku Maezawa in which he promised to give away vast sums of money to retweeters, one commemorating the passing of the actor Chadwick Boseman, and one by an American teenager begging the fast-food outlet Wendys for free chicken nuggets. That was not a paragraph I ever expected Id type.

Crucially though, I would not classify any of the above as truly viral in nature, other than perhaps Carter Wilkerson, the nuggets guy. All the others were broadcast by accounts with an extremely high following, from which almost all shares directly followed. Wilkersons plea for free nuggs, on the other hand, picked up gradual momentum over the course of a month as more and more people saw the humorous story the David vs Goliath angle of a man attempting to achieve a truly impossible goal and began to talk about the story and share it. Thats what we all mean by a virus, isnt it? Something that starts slowly and builds remarkably quickly due to fertile conditions for spreading. Im no epidemiologist, but I dont think there has ever been a biological virus that started by being transmitted simultaneously to millions of people from the same one original source. Admittedly most of my knowledge in this area comes from watching the 2011 movie Contagion repeatedly, but I still think Im correct on that one.

We could consider everything that goes viral on the internet to be on a scale of