Four distinct points are marked in a line. For each point, the sum of the distances from said point to the other three is calculated; getting in total 4 numbers. Decide whether these 4 numbers can be, in some order: a) $29,29,35,37$ b) $28,29,35,37$ c) $28,34,34,37$
2013 Cono Sur Olympiad
Day 1
In a triangle $ABC$, let $M$ be the midpoint of $BC$ and $I$ the incenter of $ABC$. If $IM$ = $IA$, find the least possible measure of $\angle{AIM}$.
Nocycleland is a country with $500$ cities and $2013$ two-way roads, each one of them connecting two cities. A city $A$ neighbors $B$ if there is one road that connects them, and a city $A$ quasi-neighbors $B$ if there is a city $C$ such that $A$ neighbors $C$ and $C$ neighbors $B$. It is known that in Nocycleland, there are no pair of cities connected directly with more than one road, and there are no four cities $A$, $B$, $C$ and $D$ such that $A$ neighbors $B$, $B$ neighbors $C$, $C$ neighbors $D$, and $D$ neighbors $A$. Show that there is at least one city that quasi-neighbors at least $57$ other cities.
Day 2
Let $M$ be the set of all integers from $1$ to $2013$. Each subset of $M$ is given one of $k$ available colors, with the only condition that if the union of two different subsets $A$ and $B$ is $M$, then $A$ and $B$ are given different colors. What is the least possible value of $k$?
Let $d(k)$ be the number of positive divisors of integer $k$. A number $n$ is called balanced if $d(n-1) \leq d(n) \leq d(n+1)$ or $d(n-1) \geq d(n) \geq d(n+1)$. Show that there are infinitely many balanced numbers.
Let $ABCD$ be a convex quadrilateral. Let $n \geq 2$ be a whole number. Prove that there are $n$ triangles with the same area that satisfy all of the following properties: a) Their interiors are disjoint, that is, the triangles do not overlap. b) Each triangle lies either in $ABCD$ or inside of it. c) The sum of the areas of all of these triangles is at least $\frac{4n}{4n+1}$ the area of $ABCD$.