Is this math/geometry problem really that difficult? (OECD)

[jmowreader]

8. 99 cm.

One-sixth of the diameter of the circle is 104.67 cm, and just for GP let's round down to 104.

Now let's throw in a piece of information that's NOT in the question: how a revolving door is made and weatherstripped. These doors are made out of three two-inch-thick door slabs, and there's a piece of felt weatherstripping running right down the middle of each door slab. (At least that's how the only revolving door in town is made.) If you want the wind to not whip through the door assembly, you need to have half the thickness of the door slab (2.5 cm) between the gasket and the edge of the door opening on both sides of the door opening...so, take your 104cm "ideal" hole and reduce it by 5cm, leaving us a 99cm door opening.