Stage: 1 Challenge Level: 
Arrange three red, three blue and three yellow counters into a three-by-three square grid, so that there is only one of each colour in every row and every column.
Working systematically. Counters. Practical Activity. Visualising. Interactivities. Investigations. Addition & subtraction. Factors and multiples. Multiplication & division. Combinations.
Published October 1999.
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