Maths on the Back of an Envelope
By Rob Eastaway
Published by HarperCollins in 2019
How many cats are there in the world? What's the chance of winning the lottery twice? And just how long does it take to count to a million? This book takes an entertaining look at how to figure without a calculator. Packed with amusing anecdotes, quizzes, and handy calculation tips for every situation, Maths on the Back of an Envelope is an invaluable introduction to the art of estimation, and a welcome reminder that sometimes our own brain is the best tool we have to deal with numbers..
Behind the scenes:
I'd been doing a school talk with this title for ten years, but it took me a long time to figure out how to create a book that combines estimation with more exact arithmetic, while keeping the content light in tone. I spent a long time debating the title with the publisher, especially as envelopes are dying out, but in the end we stuck with this one - and judging from the positive reaction it got from the maths, business and engineering community, it was the right decision.
The first hardback edition of the book sold out inside a month, and the re-print allowed me to correct some annoying typos that had crept into the first batch. So, if you find yourself with a copy of the book that declares that 43 x 5 = 115, you are the possessor of what I hope will become a rare first edition.