Stage: 2 Challenge Level: 
How are you going to start?
How much longer does the 11-minute timer take than the 7-minute timer?
How much longer does the 11-minute timer take than the 7-minute timer?
Factors and multiples. Interactivities. Practical Activity. Visualising. Working systematically. Addition & subtraction. Combinations. Multiplication & division. Investigations. Trial and improvement.
Published May 2000.
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