Activity: Adding 3-digit and 2-digit numbers Complete this interactive activity to understand how to add numbers using column addition. Then put your knowledge to the test!

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 ...

If you can add two 3-digit numbers, then you can use the same method to add 4-digit numbers together. Just remember to add on the number that you have regrouped.