I am currently in my 12th year of teaching maths, and it scares me just how little I really understand about the subject I love.   Why are eleven and twelve not called one-teen and two-teen? Why does a negative times a negative equal a positive? Why can I just flip the second fraction over and change to a multiply when I want to divide? Why does the Venn diagram method produce the highest common factor and lowest common multiple of two numbers? Why is the volume of a pointed shape equal to a third of the volume of the full shape?   I kind of know the answer to these, and I can carry out the skills relatively comfortably myself (unless it is a really nasty fraction, of course), but that is no real help when I am trying to introduce the topic to students and they are asking me why. Now, thanks to Ed's book, I have the answers and a whole lot more besides.   For this is not just a book packed full of fascinating facts. Scattered through the pages are practical teaching tips that can be used straight away in the classroom.Having read the book, I don't just have more answers to students' questions, I also have new ways of introducing and extending topics, and a much more in depth knowledge of a subject I thought I knew pretty well.   Personally, I would make this book compulsory for all trainee teachers, all NQTs, all maths teachers, all Heads of Department, and all Senior Leaders. Basically, everyone.

I just wish I had negotiated some kind of commission deal!.