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Poland - Second Round
2024 Poland - Second Round
4
4
Part of
2024 Poland - Second Round
Problems
(1)
Regular hexagon combo
Source: Polish MO Second round 2024 P4
2/10/2024
Let
n
n
n
be a positive integer. A regular hexagon
A
B
C
D
E
F
ABCDEF
A
BC
D
EF
with side length
n
n
n
is partitioned into
6
n
2
6n^2
6
n
2
equilateral triangles with side length
1
1
1
. The hexagon is covered by
3
n
2
3n^2
3
n
2
rhombuses with internal angles
6
0
∘
60^{\circ}
6
0
∘
and
12
0
∘
120^{\circ}
12
0
∘
such that each rhombus covers exactly two triangles and every triangle is covered by exactly one rhombus. Show that the diagonal
A
D
AD
A
D
divides in half exactly
n
n
n
rhombuses.
combinatorics