Stage: 2 Challenge Level: 
You have two egg timers.
One takes 4 minutes exactly to empty and the other takes 7 minutes.
What times in whole minutes can you measure and how? (You can ignore the time it takes to reset the timers.)
Practical Activity. Investigations. Interactivities. Trial and improvement. Working systematically. Visualising. Multiplication & division. Combinations. Factors and multiples. Addition & subtraction.
Published March 1998.
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