When I was growing up, we used slide rules in the advanced math classes. My father was an engineer at Boeing and used various types of them. When my mom passed away and I was going thru all the drawers in my dad's desk I found a bunch of them. My daughter teaches 4th and 5th grade - I was hoping to show the kids the antique calculators - but I could not for the life of me remember how to do it. Nor could I find anyone that knew how. It has been 40 years since I had used one - my dad was adamant that we know how so we could double check the calculator. It didn't occur to me Google it and I let them all go.