What are different number systems used in different countries?
The numbering systems you mention are all obsolete. For example, Roman numerals are only used for affect now, e.g. “Super Bowl XLVII”, never for mathematical computations, when they are quite cumbersome. When it comes to numbers, everyone speaks the same language now. However, if you are researching ancient number systems, I think the Mayans had a very interesting one. Their system was basically a positional system like the one we all use now, except it was in base 20, which I suppose means they used their toes as well as their fingers for counting. They even had a representation for the number zero. Considering the period when the Mayan civilization flourished, their system was quite modern.
