MathDB
Changing the colour of all cells in a column or row

Source: Baltic Way 2007

November 30, 2010
combinatorics proposedcombinatorics

Problem Statement

We are given an 18×1818\times 18 table, all of whose cells may be black or white. Initially all the cells are coloured white. We may perform the following operation: choose one column or one row and change the colour of all cells in this column or row. Is it possible by repeating the operation to obtain a table with exactly 1616 black cells?
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