Just helped my neighbour bury a rolled-up carpet in the woods. She said her husband would have done it but he is out of town. Good deed done for the day!
So, there’s a college math student, and one day, there’s a terrible snowstorm, but the college doesn’t close. So she goes to the effort to clean off her car and force her way through the nearly-impassable streets, and gets to her math class forty minutes late. The boards are all covered floor to ceiling with equations, and there’s only one other student in the entire lecture hall.
She sits down next to the other student and asks “What’s he talking about?”. The other student answers “I don’t know, I only got here five minutes ago.”
(called to mind because Thursday, in my last-period math class, only one student was present at the start of class)
To amplify a bit, it sort of is a math joke because math professors use the blackboard probably more than those of any other discipline. But it is basically an oblivious professor joke.
Brings to mind the one about the griping dean: “Why can’t you be like the math department? They just ask for pencils and paper and wastebaskets. Or the philosophy department; they only ask for pencils and paper.”
“The boards are all covered floor to ceiling with equations” would imply the lecture has been going on for quite a bit longer than the five minutes the other student has been there.