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Double Digit Addition using Decomposition

Solving an equation using multiple methods is a huge part of the Common Core. Students must be able to show their thinking and show multiple ways to get to the correct answer. One of my favorite methods for teaching addition is by decomposing numbers using number bonds.


Decomposing Numbers: Decomposition Addition Pack!

I begin with students practicing breaking apart a two digit number using a number bond (see picture above). I then introduce the decomposition addition method (first without regrouping, then with regrouping). I take a few days (even a week if needed) to really practice the method without regrouping before I introduce it with regrouping. When you need to regroup, there’s a few extra steps involved. Here is a sample anchor chart that I put up in the classroom:fullsizerender-4

It seems overwhelming at first, but it’s really simple and helps students truly understand numbers! slide05slide06

I’ve created a decomposition addition pack on TPT to help you teach this method. It includes mini anchor charts/posters, a sorting page, multiple practice worksheets for decomposition with and without regrouping, two assessments, and answer keys. The above pictures are part of the product, and you can view and download the product here:

Decomposing Numbers: Decomposition Addition Pack!

Enjoy and let me know how your students like adding with this method!

-Mrs. B