Why do buses come in threes?

the long version

Rob Eastaway and Jeremy Wyndham take you on a mesmerizing journey through the logic of life in a quest for the hidden mathematics in everyday events. It's a world in which Newton's laws explain bar fights and there may be solid reasons why your shower always runs either too hot or too cold. Did you think it was all a matter of coincidence? Universal randomness? To put it in a more philosophic perspective: Is bad luck just chance--or can it be explained? Whether you have a hardcore science background or haven't added up a column of figures in years, this book will entertain you as it illuminates corners of human experience that have long seemed dark and mysterious.--From publisher description.