Maths on the Back of an Envelope

‘A delightfully accessible guide to how to play with numbers’ – Dr Hannah Fry, author of Hello World and The Mathematics of Love

‘Put aside those calculators and computers, and find a pen and piece of paper! In a collection of riveting tips and examples, Eastaway shows us amazing short-cuts to get rough answers to important questions. I still find it remarkable that 16% of 25 is exactly the same as 25% of 16!’ – Professor Sir David Spiegelhalter, author of The Art of Statistics

‘Another terrific book by Rob Eastaway’ – Simon Singh

‘Packed with fun examples and fresh ideas. I thought I was on top of this subject, but I learned a lot’ – Tim Harford

‘A joyful primer about the lost art of calculating without a calculator’ – Guardian

Rob Eastaway is a writer, speaker and consultant. His books include the bestselling What is a Googly? and Why Do Buses Come In Threes? He jointly devised the system now used to officially rank international cricketers and lives in London, where he is a keen weekend cricketer and occasional golfer.