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: 3

2013 Indonesia MO, 1
Tags: geometry , combinatorics , parallelogram , elementary counting , rectangle
In a $4 \times 6$ grid, all edges and diagonals are drawn (see attachment). Determine the number of parallelograms in the grid that uses only the line segments drawn and none of its four angles are right.

2013 India Regional Mathematical Olympiad, 1
Tags: composition , digit sum , elementary counting
Find the number of eight-digit numbers the sum of whose digits is $4$

2015 Moldova Team Selection Test, 4
Tags: combinatorics , elementary counting
In how many ways can we color exactly $k$ vertices of an $n$-gon in red such that any $2$ consecutive vertices are not both red. (Vertices are considered to be labeled)