A little off topic but here it goes:
Took a high school shop class and the school put a gym teacher in charge:
First day of school, teacher was sitting in his chair playing with a retractable tape measure, pulling it out and letting go. Bell sounds and he asked" is there anybody here that can read a tape measure?" Out of about 20 dudes, three hands went up including mine. Ok, show us how he said? Guy next to me sez, he's looking at you! So I get up grab the chalk and drew two big lines on the board and said "that's and inch!"
Everybody including the teacher laughed, though I was an idiot! I said wait!
I drew another line on the board but not quite as long between the two other lines, and wrote 1/2-inch twice, not so many laughing now then more lines, that's a 1/4-inch. Then I turned to the gym teacher and said how far do you want this to go? He had quit playing with the tape measure and I noticed he was looking at the tape.
I can't recall if he said "Good job or Not!"
Grandpa gave me that education on a fold-old ruler that came out of a pocket on his overalls, and I'm forever grateful!
Never mastered the slide rule.