Mathematics has a reputation of being dull and difficult. Here is an antidote. This lively exploration of arithmetic considers its basic processes and manipulations, demonstrating their value and power and justifying an enduring interest in the subject. With humour and insight, the author shows how basic mathematics relates to everyday life – as true now as when this book was originally published in 1940. The introductory treatment of millions, billions and even trillions could be profitably read by aspiring bankers, economists or politicians. H. G. Wells is gently teased for his mistake in applying the law of proportionality in a novel. McKay politely adjusts the astronomical scales selected by the eminent cosmologist Sir James Jeans. He confidently navigates the hazards of averages, approximations and units. For anyone interested in what numbers mean and how they can be used most effectively, this book will still educate and delight.