Stage: 2 Challenge Level: 
Can you work out which number is used twice? This will get you going.
How can you keep a check on which numbers you have used?
You could print off this sheet which has two copies of the puzzle on it.
Interactivities. Working systematically. Divisibility. Addition & subtraction. Factors and multiples. Multiplication & division. Investigations. Visualising. Trial and improvement. Combinations.
Published September 2001,May 2009.
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