We are all doing math all the time, from the way we communicate with each other to the way we travel, from how we work to how we relax. Many of us are aware of this. But few of us really appreciate the full power of math - the extent to which its influence is not only in every office and every home, but also in every courtroom and hospital ward. In this eye-opening and extraordinary book, Kit Yates explores the true stories of life-changing events in which the application - or misapplication - of mathematics has played a critical role: patients crippled by faulty genes and entrepreneurs bankrupted by faulty algorithms; innocent victims of miscarriages of justice and the unwitting victims of software glitches. We follow stories of investors who have lost fortunes and parents who have lost children, all because of mathematical misunderstandings. Along the way, Yates arms us with simple mathematical rules and tools that can help us make better decisions in our increasingly quantitative society