Cover a board with three types of dominoes
Source: IMOC 2022 C3
September 5, 2022
combinatoricsdominoes
Problem Statement
There are three types of piece shown as below. Today Alice wants to cover a board with these pieces without gaps and overlaps. Determine the minimum number of pieces should be used to cover the whole board and not exceed the board. (There are an infinite number of these three types of pieces.)
[asy]
size(9cm,0);
defaultpen(fontsize(12pt));
draw((9,10) -- (59,10) -- (59,60) -- (9,60) -- cycle);
draw((59,10) -- (109,10) -- (109,60) -- (59,60) -- cycle);
draw((9,60) -- (59,60) -- (59,110) -- (9,110) -- cycle);
draw((9,110) -- (59,110) -- (59,160) -- (9,160) -- cycle);
draw((109,10) -- (159,10) -- (159,60) -- (109,60) -- cycle);
draw((180,11) -- (230,11) -- (230,61) -- (180,61) -- cycle);
draw((180,61) -- (230,61) -- (230,111) -- (180,111) -- cycle);
draw((230,11) -- (280,11) -- (280,61) -- (230,61) -- cycle);
draw((230,61) -- (280,61) -- (280,111) -- (230,111) -- cycle);
draw((280,11) -- (330,11) -- (330,61) -- (280,61) -- cycle);
draw((280,61) -- (330,61) -- (330,111) -- (280,111) -- cycle);
draw((330,11) -- (380,11) -- (380,61) -- (330,61) -- cycle);
draw((330,61) -- (380,61) -- (380,111) -- (330,111) -- cycle);
draw((401,11) -- (451,11) -- (451,61) -- (401,61) -- cycle);
[/asy]
Proposed by amano_hina