Tanya Khovanova recounts an amusing trick she learned from John Conway: how to count the number of steps in a stairway. The obvious answer is to just count them as you walk up the stairs but there’s an additional stipulation: count them like a nerd would.
The basic idea is to first determine the number of step modulo 10 and then estimate the how many groups of 10 steps there are to determine the total number. I’ll let you read Khovanova’s post to see the trick for finding the steps mod 10.
There’s not really anything exciting here but it did strike my fancy for some reason. Perhaps you’ll enjoy it too.