Bought it because I thought I had forgot how to do "long division.In fact I had forgot how to show the working out.The author (like me) did 'nt show working out.Also a young person told me they multiply "using grid".The book explained simply,what this was.Given the book to my youngest son,he is doing workshop engineering,and finds its easy explanations useful to his job ! Have other titles in the "dummies" range,all make hard topics easy to understand.Would recommend,for refreshing your own maths,or for anyone else that finds the subject difficult.