moondrek

That is indeed one of the many hazards and risks which pre-modern states seemed to have grappled with, according to the linked blog series. You may find the series to be an interesting read to see one historian's overview on how pre-modern states were to varying degrees exposed to, managed, and suffered the consequences of, said risk!

Have you considered just budgeting yourself $600/month on guilt-free non-essential transportation, and committing to spending any remainder on nice refreshments/gifts for your friends?

I read it as the students being familiar with a similar "trick" question and erroneously pattern matching on that.

Another similar riddle goes like:

"If it takes 5 machines 5 minutes to make 5 widgets, how long would it take 100 machines to make 100 widgets?"

The correct answer there being "5 minutes", and the intuitive wrong answer being "100" as per your post.

That would make sense as to why the teacher also expected "3", since they should be familiar with the existence of their non-intuitive questions, even if they misremember the specific non-intuition.

The video game "To The Moon" and its sequels/related media explores this premise.