1
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I'm open and not closed

or closed but not open.

If I'm not, though I can be,

open and closed

or neither closed nor open.


Hint: math

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  • 5
    $\begingroup$ I'm voting to close... or open... ARGH, I'M SO CONFUSED! ;-) $\endgroup$ – Stiv Nov 22 '19 at 22:39
  • $\begingroup$ Hopefully the answer is not related to body part of seniors.. $\endgroup$ – Alex Nov 22 '19 at 23:11
  • $\begingroup$ @Alex rot13(vg vf abg) :) $\endgroup$ – jazhang Nov 23 '19 at 1:14
3
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Sets? Because they can be open, closed, both or neither open or closed?

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2
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Are you a(n)

interval?

I'm open and not closed

If an interval does not contain its endpoints it is open.

or closed but not open.

A closed interval does contain its endpoints.

If I'm not, though I can be,

open and closed

A half-open interval contains only one of its endpoints.

or neither closed nor open.

A degenerate interval only consists of one real number.

Hint:

An interval in math is a set of (real) numbers lying between the extremities.

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  • $\begingroup$ hmm, this wasn't my original intention. The 'thing' could be both open and closed or neither closed nor open. I've edited the puzzle to reflect this clarification $\endgroup$ – jazhang Nov 23 '19 at 1:10
  • $\begingroup$ @jazhang Next guess? $\endgroup$ – S.S. Anne Nov 23 '19 at 1:22

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