If memories of learning algebra bring you out in a cold sweat and thoughts of quadratic equations cause you feelings of fear and dread, I Used to Know That: Maths can help. A light-hearted and informative reminder of the things that we learnt in school but have since become relegated to the backs of our minds, this book will help you to brush up on your mental arithmetic, including percentages, averages and recurring decimals or work on your trigonometry skills, from Pythagoras' theorem to triangle areas and angles. A practical guide to turn to when an answer is eluding you, from helping a child with homework to calculating change or understanding statistics. I Used to Know That: Maths is a fun and accessible way to re-visit all those useful tips and maths tricks that you have forgotten from your school days.