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?

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 .