Tape measure: That reminded me of something that happened years ago. I was training the bosses son on some shop equipment like a lathe. We needed a 1/4 inch cut, so I told him to set the machine to cut 1/8" from where it was set. "Don't you mean 1/2"?" What do you mean by that? "2 is half of 4."
I layed out an inch, large scale on a piece of paper, had it scaled at 1/16th inch marks. He got the half and the quarters. But didn't know about the 16ths or 8ths. Thought they were extra marks put there to make the tape look good.