MathDB
VMO 2018 P3

Source: Vietnam MO 2018 1st day 3rd problem

January 11, 2018
geometryinequalitiescombinatorial geometry

Problem Statement

An investor has two rectangular pieces of land of size 120×100120\times 100. a. On the first land, she want to build a house with a rectangular base of size 25×3525\times 35 and nines circular flower pots with diameter 55 outside the house. Prove that even the flower pots positions are chosen arbitrary on the land, the remaining land is still sufficient to build the desired house. b. On the second land, she want to construct a polygonal fish pond such that the distance from an arbitrary point on the land, outside the pond, to the nearest pond edge is not over 55. Prove that the perimeter of the pond is not smaller than 440202440-20\sqrt{2}.