by Rob Eastaway
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3. Discrepancies like this are common, because the attendances reported by clubs are typically the number of tickets sold, including debenture and season tickets, rather than the number of bodies that turned up on the day.
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4. In the 2016 Olympics in Rio, Charlotte Dujardin surpassed her London score, achieving an impressive 93.857% to claim gold once again.
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5. In the USA, 98.6 °F is still the figure commonly used. In the UK, the commonly used figure in my parents’ generation was 98.4 °F. Fahrenheit has now dropped out of fashion in the UK, and doctors have reverted to 37 °C as the norm.
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6. According to Susan Loynes, an Electoral manager who worked on the count, the Kensington recounts were all within five of each other, and the variation was entirely down to judgements about spoiled ballot papers. Given the small variation, the Conservatives were clutching at straws when they requested the third recount.
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7. There are some markets that can be extremely sensitive. A friend who worked in the retail (petrol station) side of one of the major oil companies reckoned that if they priced petrol at, say, 132.9p per litre, while a competitor next door was charging 0.1p less at 132.8p, that difference of less than 0.1% in the price could lose them at least 5% of their custom.
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8. Five hundred thousand was the worst-case scenario in a forecast by the European Union Scientific Steering Committee in 1996.
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2: TOOLS OF THE TRADE
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1. Though, to be fair, most mathematicians would be able to work that out.
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2. The ‘1’ being carried represents 10. Where you place that little 1 depends on where you went to school and what the standard practice was at the time.
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3. The Times Tables Rockstars website, created by Bruno Reddy, records pupils’ performances every time they practise their times tables. There are over one billion items in their database, most of them still not analysed.
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4. In most news stories, percentages are quoted to two significant figures, and even when they are quoted to three, two significant figures is normally enough. For example, a story in front of me now talks about recycling rates of 44.8%. If the story had said 45% instead, would we have felt any less well informed?
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3: EVERYDAY ESTIMATION
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1. Spreadsheets are a minefield for potential errors. One of the most common is when a formula is entered to ‘sum’ a column, but using the wrong range of cells, so that cells at the top or bottom are missed from the total.
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2. The Rule of 72 applies to other things that grow, such as populations. If the world population is growing at 1.2% per year, it will be 72 ÷ 1.2 = 60 years before there are twice as many people on the planet as there are now.
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3. This is only because of the historical decision of what level to set the pound at. It does not reflect the relative wealth of the countries!
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4. A commonly used approximation for pi is 22 ÷ 7, which is remarkably accurate (it’s within 0.04% of the correct value of pi!). But if you want to learn pi to more decimal places, there are several mnemonics, of which my favourites are: ‘How I wish I could calculate pi’ and ‘May I have a large container of coffee.’ In each case, count the number of letters in each word to give the digits of pi to several decimal places.
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5. The width of a lane is actually 1.22 metres. Like most dimensions in sport, it was originally specified in a nice round number of imperial units: 1.22 metres = 4 feet.
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6. Details of this episode seem to have been lost in the archives; this is our joint best attempt at recalling the details of what we saw.
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7. I know this because my friend Aoife Hunt had to do it, when researching crowd logistics.
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8. In 2008, 5.7% of the Welsh were called Jones according to the journal Significance.
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9. One such is known as ‘least-squares’ regression.
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10. Source of data: Global/Data analysis.
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4: FIGURING WITH FERMI
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1. Any other town with a population well over 100,000 will do instead.
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2. Though see here for why published attendances at football matches overstate the real figure.
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3. The 80:20 rule, more formally known as the Pareto principle, is a rule of thumb that suggests that 20% of the population owns 80% of the resources. It applies – very crudely – to many situations, including the distribution of wealth in countries and, very likely, to the attendances at football matches.
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4. There are conflicting reports of how many balls were in the Bulgarian lottery. The five million figure is on the basis that there were 42 balls in the lottery. Other sources suggest there were 49 balls in the Bulgarian lottery in question, in which case the odds of a repeat of the numbers was 14 million to one.
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5. The number of different pairs of dates that can be chosen out of a list of N dates is 1/2 × N × (N – 1). In this case N = 75 and the total number of pairs is 2,775
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6. According to the National Records of Scotland, in 2018 there were 275 babies named Alexander out of a total of 24,532 baby boys born in the year.
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7. It was a BBC World Service edition of More or Less in January 2018 – you’ll find it online.
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8. As calculated by Peter Rowlett in Aperiodical, November 2013.
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9. In central London it varies from WC1 to WC2 of course.
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10. If you’re French, 1,204 is the even punchier: mille deux cents quatre.
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11. Linguistics experts call the word ‘like’ a discourse marker, and have found that it plays a more important role in speech than fillers such as ‘um’ and ‘er’. See, for example, ‘Placing like in telling stories’, Jean Fox Tree, 2006.
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12. It reportedly cost the Ministry of Justice £90,000 in admin and Leicester Council £85,000 in legal fees.
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ACKNOWLEDGEMENTS
This book has been a long time in the making. I first contemplated writing it several years ago, yet it took a coffee with Wendy Jones to finally push me into action, and I’d like to thank her for being a great sounding board in the early stages.
My thanks to Hugh Hunt and John Haigh with whom I regularly have back-of-envelope jousts and who inspired a couple of the examples in the book. Graham Cannings, Chris Healey, Chas Bullock and Andrew Robinson provided invaluable critiques of the first draft, while Rose Davidson, Geoff Eastaway, Pete Sanders and Rachel Reeves provided equally helpful comments on the second. Special thanks to my mentor Dennis Sherwood for helping me to see the big picture and for sharing your deep insights on precision and the abuse of statistics.
I was lucky to be able to tap into some valuable expertise when I needed it, particularly from Claire Milne, Aoife Hunt, Jay Nagley and Ian Sweetenham, and also from Tom Rainbow and Catherine van Saarloos who are doing great work promoting Core Maths in schools.
My wonderful wife Elaine has been ever-present and ever-patient when I’ve sought advice on everything from grammar to subtitles.
Thank you Timandra Harkness for reminding me about the cats.
And finally, thanks to the team at HarperCollins, in particular Ed Faulkner who so enthusiastically picked up on this book, and to my lovely editor Holly Blo
od, who has so professionally filled the dual role of constructive critic and supportive cheerleader.
ABOUT THE AUTHOR
Rob Eastaway has written or co-written twelve books, including the bestselling Why Do Buses Come in Threes? and Maths for Mums and Dads as well as What Is a Googly?, the acclaimed beginner’s guide to cricket. He is the Director of Maths Inspiration, a national programme of theatre-based lecture shows for 15–17 year olds that has reached over 150,000 teenagers since it began in 2004.
Rob regularly gives talks to all age groups in primary and secondary schools, appears on BBC Radio 4’s current affairs/numbers programme More or Less, and works closely with National Numeracy, the national charity that campaigns for better adult numeracy.
In 2017, Rob received the Zeeman medal for excellence in communication of maths to the general public.
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