Is it possible to find a subset $A$ of the real line $\mathbb R$ such that the Lebesgue measure of $A$ minus its interior is positive ?
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See here for an equivalent, more general question. Note that $\partial A = \overline A \setminus A^\circ$; the frontier is the set minus its interior. – AlexR Aug 19 '14 at 14:47
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@AlexR : Usually, $\partial A=\overline{A}\setminus A^°$, doesn't it ? – Student Aug 19 '14 at 14:50
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1thanks. Still chosing a closed set you remain equivalent :) – AlexR Aug 19 '14 at 14:52
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A fat Cantor set. A is closed, its interior is empty, so $A$ minus its iterior is $A$ itself. See previous question: https://math.stackexchange.com/a/287872/442