Yes, I see what you mean. To me, doing those sorts of calculations by hand is just really fun. I agree with you about the importance of applying logical rules i

Yes, I see what you mean. To me, doing those sorts of calculations by hand is just really fun. I agree with you about the importance of applying logical rules in this way. Thanks for this suggestion, maybe I'm going to add a paragraph about the slide rule as an afterthought later on :D