MathDB
tiles 3x1 and 2-1 in 7x 7board

Source: 2018 Argentina OMA Finals L3 p3

May 14, 2024
geometrycombinatoricscombinatorial geometrytilesTiling

Problem Statement

You have a 7×77\times 7 board divided into 4949 boxes. Mateo places a coin in a box.
a) Prove that Mateo can place the coin so that it is impossible for Emi to completely cover the 4848 remaining squares, without gaps or overlaps, using 1515 3×13\times1 rectangles and a cubit of three squares, like those in the figure. https://cdn.artofproblemsolving.com/attachments/6/9/a467439094376cd95c6dfe3e2ad3e16fe9f124.png b) Prove that no matter which square Mateo places the coin in, Emi will always be able to cover the 48 remaining squares using 1414 3×13\times1 rectangles and two cubits of three squares.