Stage: 2 Challenge Level: 
Try placing the numbers $1$, $5$ and $7$ first.
Which rows/columns have an odd product?
Which are not divisible by $3$?
Multiplication & division. Working systematically. Factors and multiples. Addition & subtraction. Interactivities. Divisibility. Visualising. Investigations. Common factors. Combinations.
Published October 2002.
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