From two renowned mathematical geniuses, a professor and a columnist for "Scientific American", comes an accessible guide to mentally calculating maths at lightning speed and amazing ease. All the secrets of easy mental arithmetic are revealed, and the secrets to incredible memorisation and other feats of mind, making it easy to perform maths tricks for the real world: from calculating restaurant tips to working out gambling odds. It is an accessible and easily understood guide to using mental mathematics in everyday life; whether shopping, gambling, adding up commission. It ties in with the topical fascination with puzzles, sudoku and games of mental stimulation.