You could be teaching here at the University of Cape Coast in Lecture theatre 21 where the room is labelled with the last bit of ink in the marker.
You could get two hundred and fifty in a room like this, and then, if you can squeeze the marker hard enough to get any more ink out of it, get some equation engraved into the "white" board (more of a dirty grey metal, actually). But don't be too surprised if the student in the back corner can't even find the whiteboard, not to mention read anything on it. You could try using slides....but they are smaller. Perhaps just one letter, erase, next letter, ....?
