2007 AMC 8 Problems/Problem 9
Problem
To complete the grid below, each of the digits 1 through 4 must occur once in each row and once in each column. What number will occupy the lower right-hand square?
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cannot be determined
Solution
The number in the first row, last column must be a due to the fact if a
was in the first row, second column, there would be two threes in that column. By the same reasoning, the number in the second row, last column has to be a
. Therefore the number in the lower right-hand square is
.