I got asked a variation on this in an interview several decades ago. "What is the expected waiting time for a bus that arrives on average every ten minutes and

I got asked a variation on this in an interview several decades ago. "What is the expected waiting time for a bus that arrives on average every ten minutes and you show up at a random time". I was sure it was 5 but they actually wanted me to do the math from the article, in my head, in 30 minutes. I did not pass that interview and did not get the job (which was a good thing long term). I really enjoy having 10-20 lines that produces the expectation value directly by simulation; that's a fast way for me to understand the underlying values.