Oral exam place and questions

I've been reading about oral exams for a private pilot license (in the U.S.),
and two questions have come to mind.

Where does this exam take place? Is it in a classroom, or in a testing
center, or is it actually in the aircraft?

When you are asked math-type questions, are you expected to answer with just a
ballpark figure or an exact answer? In the latter case, can you use a
calculator, or pencil and paper, or must you do it in your head?

If I'm asked how long it will take to go 84 nm at 120 kts, I know that it's
about 40 minutes, but if an exact answer is required I don't see how I could
practically provide that without a calculator.

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