Years ago when I delivered newspapers, I learned about street numbers and apartment numbers. And I remember when old mail routes were renumbered so the emergency personnel could find each residence. I guess not everyone got the memo. Several weeks ago I had the occasion to call the sheriff's department. It was after dark, and I told the deputy my address and promised to leave my porch light on. I live in a subdivision and the house number pattern is straightforward: sequential even numbers on the right and sequential odd numbers on the left. Now what is the probability that the deputy goes to the wrong house (even though I was the only one with a porch light on). Quite a few of the neighbors have numbers on their mailboxes and/or houses. The deputy pointed out that I didn't have a number on my house. "It's on the mailbox," I replied. Of course, I noticed later that a morning glory vine has mostly obscured the number. Still, no excuse for a deputy to go to a house on the right when the odd numbered houses are on the left.
Then yesterday, I encountered another person who was thrown off by a simple number pattern. First, some background--I don't clean windows often, but I had taken a notion yesterday to clean the windows of the front storm door. It's also not very often that someone rings my doorbell, either. Now what are the chances that I will be in the bathroom when someone does? Yes, I was in the bathroom when the doorbell rang. I got to the door as quickly as possible to find a lady with a pizza. She needed to be at the house next door. Then, after she left I noticed a smudge on my freshly cleaned storm door. She must have put her hand to the glass to peer in to see if I was inside since I didn't answer the door right away. What is the probability that a pizza delivery person will go the wrong house and smudge a rarely cleaned, but freshly cleaned window? (As ds would say, in this case it was a 100%!)