So something new I learnt today. The ratio of the long side to the short side of an ISO A[0-9] sheet of paper is . Why this is news to me I don’t know as it should be pretty obvious. Since the relationship from size A(n) to size A(n+1) is that the longest side is halved, and keeping the ratio of the long/short sides the same:

Well it’s a nice distraction from all the M208 group theory stuff I’m working through.