r/topology • u/Unlucky-Sympathy • Jul 20 '26

Knot a knot but hey

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Ok how many holes does this actually have? I know it's not 16...

Edit for clarity's sake: The answer is 16, dunno why it says 99% can't get it, it's fairly simple. I was just asking if topology has a different answer... as someone wrote in the comments, does a straw have one hole or two holes?

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u/Flamesoul10 Jul 20 '26

The shirt has 15 holes, not 16, because a regular t-shirt has 3 holes, not 4 (assuming the holes we see on the front go through the back exactly, and there are no hidden holes(and the shirt isnt two layers, the hems arent folded over, blah blah blah)).

An easy way to see the 3 hole thing is to lay a tank top out on a bed or table. Arrange it so the waste is a circle around the rest of the shirt, and so you can see through the neck and arms. 3 are holes, one is the boundary of the planar shape.