This website contains problems from math contests. Problems and corresponding tags were obtained from the Art of Problem Solving website.

Tags were heavily modified to better represent problems.

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Found problems: 2

1970 Putnam, B3

A closed subset $S$ of $\mathbb{R}^{2}$ lies in $a<x<b$. Show that its projection on the $y$-axis is closed.

1975 Putnam, B4

Does a circle have a subset which is topologically closed and which contains exactly one point of each pair of diametrically opposite points?