Technology - A Mechanical Calculator
He uses plywood gears to add and subtract numbers How I built a Mechanical Calculator - YouTube
Hello Everybody! My name is Iurii, and I am a middle school Science teacher. Here I post interesting Science lesson resources - games, experiments, riddles, videos, activities, etc. I hope you'll find them useful! See my TeachersPayTeachers page https://www.teacherspayteachers.com/Store/Iurii-Galadzhun