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2010 AIME II Question 11

AIME · 2010 AIME II

Question 11

Define a *T-grid* to be a $3 \times 3$ matrix which satisfies the following two properties:

$(1)$ Exactly five of the entries are $1$’s, and the remaining four entries are $0$’s.

$(2)$ Among the eight rows, columns, and long diagonals (the long diagonals are $\{a_{13}, a_{22}, a_{31}\}$ and $\{a_{11}, a_{22}, a_{33}\}$), no more than one of the eight has all three entries equal.

Find the number of distinct *T-grids*.