well yeah, because 1/8" is 3.175mm
1/3 of a mm is a distance between 1/64" and 1/128"
mechanical pencil lead is only about 0.4mm
I still don’t see how a calculator helps though.
don’t ask me ask the person who posed the “what’s a third of 9.5mm” question
even if you’re in a situation where it’s somehow possible to manually draw 1/3 of a mm to any accuracy, 1/3 scale draft rulers still exist for metric, so it’s equivalent
because as soon as you have access to a calculator, “off the top of your head” is an irrelevance