My little warrior isn’t too smart, and she’s illiterate, but one thing she can do is work out basic fractions, because another character took the time to show her how. She can’t count too high. Her counting system itself is simple, a bit like this, but she knows what a half is. Whenever she counts in fractions, or reckons up treasure correctly when sharing it out, she remembers her friend, who’s no longer there, and misses her. Thanks, Vestra!
Fractions are important to her because she works out her tithes herself, rendering unto Humakt that which was other people’s. They are far more important to other people in her group; the follower of Issaries is far better at addition, subtraction, and multiplication than the friend who originally taught my PC.
Even a thing that is relatively simple, and is taught to children everywhere in the real world is a mystery within Glorantha. I wonder rather what the first myths about fractions are, and if there are myths about higher mathematics. Surely, in a world where tax demons can exist, there is room for calculus spirits.
Navigational methods can need maths, but I’m not sure how to apply that in a world where the stars can swerve in their courses. Maybe you rely only on the landmarks. Maybe certain stars are always reliable. Polaris stays in position, but can’t always be seen. The Red Moon can be seen from far further away than should be possible, if physics were physics.
Glorantha is cool, because it’s a place where myth is more important than physics. I’m pretty sure that myth is more important than maths, too, although I haven’t yet seen an example.