MathDB

2

Part of 2021 Chile National Olympiad

Problems(1)

array of the digits 1,2,..., 9 in the shape of an X J

Source: 2021 Chile National Olympiad level 2 p2, level 1 p4

10/22/2022
A design XX is an array of the digits 1,2,...,91,2,..., 9 in the shape of an XX, for example, https://cdn.artofproblemsolving.com/attachments/8/e/d371a2cd442cb7a8784e1cc7635344df722e20.png We will say that a design XX is balanced if the sum of the numbers of each of the diagonals match. Determine the number of designs XX that are balanced.
combinatorics