Fun maths teasers and brain-bending puzzles from TV boffin Johnny Ball, from his slot of the same name on Zoe Ball's Radio 2 show. Designed to twist your brain into enjoyable knots of empuzzlement and designed for every level of difficulty, there are some that can be solved in a twinkling of an eye to others that will knit your brow for hours. Learn how to cheat at a coin toss, and why it is that some parts of a high speed train travelling at 125mph are actually going backwards.