Next time a young'un has a problem with an HP RPN calculator, let the hijinks really begin by handing 'em one of these!
You knew a slide rule was going to turn up sooner or later in this thread, just like it did back in 2003. I'll come clean and humbly admit that the last time I used one of those was around the time Agnew resigned. All of the neural pathways have since atrophied and I'd stumble, bumble and fumble for a good while before I could do (/ (* 10 10) 2) or, more topically, 10 10 * 2 /.