FatNums: an alternative representation for school arithmetic | Hugonweb Annotated Link Bibliography

The idea is, rather than performing carries, just write down the "fat" number in its place.

For example, adding 1234 + 5678:

1  2  3  4
5  6  7  8
----------
6  8 10 12
6  8 11  2
6  9  1  2

The result is 6912.

Instead of carrying at each digit, you "normalize" at the end. This could be useful for elementary students struggling with the concept of carrying.