The original hindu-arabic system changed over the course of several millenia to include a zero, and the look of the numbers changed somewhat, too. I want them to compare the way they were used long ago to the way they changed into our current base-ten system. Clearly there will be many similarities, but they're not quite the same thing.

By the parts still in place, I mean things like the 360 degree circle, which is a legacy of the Babylonian system of base sixty.