We put 10 mini erasers into Ziploc bags (and stapled
them shut so ED wouldn't get into them!).
Shown here is 19 + 27. He simply lays out 19 (1 bag +9)
and 27 (2 bags +7). When he counts how many single
erasers there are he exchanges 10 singles for one bag of
10. With this and the exchange game LD seems to have
really grasped the idea of "carrying."
You might also want to check out some of the Montessori-style addition worksheets that I used with the kids as they started to do double-digit addition. (You'll find these FREE over at our new location, homeschoolden.com). The links below will take you straight there! :) ~Liesl