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. 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.
Chris Waring was born in London. After a degree in Mechanical Engineering at Imperial College London and a short yet disastrous career as a headhunter, he became a maths teacher. Since then he has taught small children and Oxbridge candidates and everybody in between. He has written I Used to Know That: Maths (2010) and From 0 to Infinity in 26 Centuries (2012) for Michael O'Mara Books. He lives in York.