Download or read book I Used to Know That written by Chris Waring and published by Michael O'Mara Books. This book was released on 2012-05-18 with total page 162 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.