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.
Addition & subtraction. Combinations. Visualising. Practical Activity. Counters. Working systematically. Factors and multiples. Investigations. Interactivities. Multiplication & division.
Published October 1999.
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