Arrange the five odd digits into a five-digit number, such that the
first two digits (as a 2-digit number) times the last two digits
(as a 2-digit number) minus the center digit results in a number composed
of repetitions of one digit. [Can the same be done with the five even
digits? - I'm guessing not - KD.]
In how many different ways can you
arrange the nine digits 1-9 in a 3x3 grid such that no square
shall have a smaller number than its own below it or to the right of it?
Source: The Best of Discover Magazine's Mind Benders, 1984. #81, #83.
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