Lo Shu Square 4 9 2 3 5 7 8 1 6

The Lo Shu Square (洛书). A magic square in which each sum of the 3 numbers in each row, column and diagonal equals 15.

Context of this book

This book on arithmetic (from the Latin "arithmetica") provides a concise yet comprehensive refresher on the elementary numerical operations of addition, subtraction, multiplication and division on integers and fractions. This book presents and organizes elementary arithmetic for a reader who is already familiar with elementary arithmetic and even some basic algebra. The author does not claim that this book is in accordance with any established or scientifically approved didactic, curriculum or educational view or approach.

Mental arithmetic

This book is about basic arithmetic concepts, not about learning "tricks" for doing quick calculations in your head. There are certainly good arguments for the importance of developing mental arithmetic skills, but real-life problems are almost never neatly arranged so that they can be solved by using handy tricks. Understanding the underlying principles is essential, whether you are doing mental arithmetic, pen and paper calculations or even using a calculator. It is important to have an understanding of what you are doing, the relationship between your calculations and the real-world problem, and how the result should be interpreted.

Nevertheless, the importance of everyone being able to at least do simple mental arithmetic is undisputed. And consistent practice is key to improving mental arithmetic skills! There are many resources available for learning mental arithmetic. I made this simple online application to practice addition, subtraction and the times tables.