"Ah. A student. I was wondering when one of those would turn up. I'm Professor Harkness, as you may have gathered." So saying, he rummages through his briefcase for some notes. "Wonderful to see you. Now, I guess that we should begin. And yes, it may be worth learning how we do things here."
Jack clears his throat, and begins. "This is like potions; there isn't much wandwork, but use of clear, plain logic and clear thinking. It's similar, but different to the Mathematics you may have learned at a Muggle school, if you have. But this is different. Muggle maths is fettered by their logical and mental, non-magical limitations. You can go to places sublime, with Arithmancy.
"Just about the only spell you'll need is the revealing spell, so we'll just practice how we do it. So, take these sheets, which have a few simple problems in the Muggle maths form for you to do, and we'll come back and show how it works."
So saying, he hands out a sheet of parchment, with two problems on, one reading 4 x 2, the other reading 18 div 3. ((These are simple. No marks deducted for using your computer calculator.))