Inch v.s Centimeter

And the legend continues on with my ex-coworker "A", an engineer~ I remember one time he came by my cubicle with a ruler in his hand, and while slapping his other hand with the ruler, he asked me the below questions: A: "Hey, are you good with rulers?" Me: "uh... well, I...guess" (what kind of question is this???) A: "OK, I am trying to [...]