When I was teaching short term in India, I learned the Hindu numerals just to get by and, when I came back, I taught my US students about them. I haven't taught them again since then, but this module has gotten me thinking. We talk in my geography and world history courses about cultural diffusion and the spread of agricultural techniques and other scientific inventions. As Seb Falk said at the end of the podcast with Neil deGrasse Tyson, when humans are in communication and they encounter conflicting explanations about how the world works, they work to reconcile them or figure out which one is wrong. This is important for humanities classrooms because they are developing networks and connections and also creating schema for how their world functions. Falk mentioned the slow movement of Hindu numbers - two centuries to get to the Islamic world and another two centuries to get to the Christian world. [Sidenote - it seems very Eurocentric to me to use non-parallel terms of Europe and Islamic, why not call it the Christian world?] He also talked about multiplying Roman numbers. I've read about merchants in Venice and nearby places who were on the vanguard of adopting the decimal system and Hindu-Arabic numbers. I think I'd have students analyze the movement of Hindu-Arabic numbers - who adopted them first, why would they have been the forerunners? They might make a map showing the diffusion of the use of Hindu-Arabic numbers.