MathDB
Paraguayan National Olympiad 2010, Level 3, Problem 1

Source:

September 20, 2014
geometry

Problem Statement

The picture below shows the way Juan wants to divide a square field in three regions, so that all three of them share a well at vertex BB. If the side length of the field is 6060 meters, and each one of the three regions has the same area, how far must the points MM and NN be from DD?
Note: the area of each region includes the area the well occupies.
[asy] pair A=(0,0),B=(60,0),C=(60,-60),D=(0,-60),M=(0,-40),N=(20,-60); pathpen=black; D(MP("A",A,W)--MP("B",B,NE)--MP("C",C,SE)--MP("D",D,SW)--cycle); D(B--MP("M",M,W)); D(B--MP("N",N,S)); D(CR(B,3));[/asy]