Column addition is a way of adding numbers together. It's helpful when you're adding two-digit or three-digit numbers together. When you do column addition, you lay out the numbers you are adding ...

You can find the difference between two numbers in more than one way. You can count up from the smaller number to the larger number. Or, you can count back from the larger number to the smaller number ...

The present paper describes the success, the methods (mental, informal written, standard algorithm) and the strategies of informal written arithmetic to be observed when 300 elementary students worked ...